Lower Cretaceous Marine Fossils, including Maccoyella sp., from the Whatarangi Formation, East Side of Palliser Bay, New Zealand

Transactions of the Royal Society of New Zealand : Geology, Volume 6, Issue 12, 18 April 1969, Page 143

Lower Cretaceous Marine Fossils, including Maccoyella sp., from the Whatarangi Formation, East Side of Palliser Bay, New Zealand

lan G. Speden

By

[Received by the Editor, January 16, 1968.]

Abstract

Fossils from four localities in the Whatarangi Formation, on the western flank of the Aorangi Range, Wellington Province, are listed. Nuculana (5.1.) sp., Pseudolimea sp., Maccoyella sp., and Rotularia sp. are described. The presence of Maccoyella indicates a Lower Cretaceous age, probably pre-Motuan, i.e., pre-Upper Albian.

Introduction

The recent discovery by Mr T. E. Bates, Victoria University of Wellington, of fossils in grits and conglomerates outcropping along the western flank of Aorangi Range, on the east side of Palliser Bay, Wairarapa, provides the first fossils known from these sediments, which from their lithological characteristics have generally been mapped in the Taitai Series (Neocomian-Aptian) (Grindley et at., 1959; Geological Map of New Zealand 1:2,000,000 [1958]; Wellman, 1959).

Bates (1968) describes the geology of the area and the stratigraphy of the Whatarangi Formation, a name proposed for a sequence of sparsely fossiliferous sandstones, grits, conglomerates, and thin-bedded sediments which are in faultcontact with older “ greywacke ” type and younger Tertiary sediments.

All specimens described and figured are held by the Geology Department, Victoria University of Wellington, and have been allotted VUW collection numbers (V), and type Mollusca (VM) and Annelida (VZ) numbers as appropriate. The abbreviations NZGS-WM and GS refer respectively to catalogues of World Mollusca and fossil collections held by the New Zealand Geological Survey, Lower Hutt.

Faunas

Fossils have been collected from four localities, two of which are represented only by stream boulders. The following are faunal lists for the collections: 1. Putangirua Stream, N165/1009, V 2085 (in place). Cerithiid gastropod indet. Brachiopod gen. et sp. indet. Polyzoa Shell fragments

2. Putangirua Stream, N165/1010, V 2086 (boulders). * Nuculana (5.1.) sp. Inoceramus prismatic shell fragments * Maccoyella sp. Chlamys (s. lat.) sp. indet. * Pseudolimea sp. Indet. bivalve fragments Cerithiid gastropod indet. Brachiopod gen. et sp. indet. Polyzoa * Rotularia sp. Plant fragments

3. Te Ika Pakeke Stream, N165/1011, V 2087 (boulders). * Maccoyella sp. Tndet. bivalve fragments Plant fragments

4. Makotukutuku Creek, Nl6B/611, V2OBB, lowest conglomerate horizon (in place). Indet. bivalve fragment Shell fragments

Paleoecology

For the most part the specimens are steinkerns and external moulds although a few pelecypod valves retain weathered calcareous shell material. No paired pelecypod valves were collected. Nearly all are broken and incomplete. Shell and plant fragments are common. An unknown amount of transportation and/or reworking has occurred, but the fragility of specimens and the presence of spines on some specimens of Maccoyella suggest that transportation has been minimal. Considering the coarse grain-size of the matrix, the preservation of ornament detail is good.

By far the commonest species is Maccoyella sp., which is represented by about 70 almost complete valves. The next most numerous species are the cerithiid gastropod (N = 8) and Nuculana (5.1.) sp. (N = 6), but polyzoan fragments are common. Most of the species followed an epifaunal mode of life, and most of the bivalves were filter feeders, but Nuculana (5.1.) sp., is infaunal and primarily a deposit feeder (Yonge, 1939; Stasek, 1961), and the indeterminable bivalve in V 2087 was probably an infaunal suspension feeder. The cerithiid gastropod was probably epifaunal, feeding on algae or diatoms attached to algae (Fretter and Graham, 1962).

The species identified indicate normal marine salinities, and the preponderance of filter feeders and polyzoan fragments suggests low or moderate turbidity (Lagaaij and Gautier, 1965). The domination of epifaunal filter-feeding species and polyzoan remains is suggestive of a high-energy hard-bottom environment at shallow depths, probably less than 300 m and perhaps of the order of 5 to 20m. The infaunal bivalves are anomalous and could indicate a soft-bottom low-energy habitat with pebbles to which epifaunal species could attach, or alternatively, could be the result of the derivation of shells from an adjacent soft-bottom environment. This second alternative is favoured by the presence of intraformational brecciated fragments of mudstone and siltstone in the grits and conglomerates, the occurrence of an indeterminable infaunal bivalve in V 2087 in a mudstone fragment, and the lack of evidence of attachment scars on pebbles. Consequently, the assemblages probably represent the mixing of elements from (1) a moderate to high-energy hard-bottom environment, the larger component and (2) a low-energy soft-bottom environment.

The uniformly small size of the specimens, including those of Maccoyella, Pseudolimea, and ?Chlamys (s.h), species of which grow to a large size, perhaps suggests derivation from juvenile or stunted populations. As the conditions were marine, derivation from juvenile populations is the more likely suggestion.

Age and Correlation

At the present state of our knowledge of New Zealand Lower and lower Upper Cretaceous faunas Maccoyella sp. is the only fossil of any importance for dating and correlating the formations of the Aorangi Range.

Maccoyella is known only from Australia and New Zealand. Besides the Aorangi species two other species occur in New Zealand. One, M. magnata Marwick, 1939, is represented by a single specimen from the type locality of the Korangan Stage (approximately Aptian) at Koranga (Wellman, 1959). It may be conspecific with M. reflecta (Moore, 1870), from the Aptian of Australia (Waterhouse, 1959). The other species, M. incurvata Waterhouse 1959, is poorly localised stratigraphically but is considered to be Lower Cretaceous (Speden, 1968).

In Australia several species have been described from the Cretaceous of the Great Artesian Basin, but only five are reasonably well known, namely Maccoyella barklyi (Moore, 1870), reflecta (Moore, 1870), umhonalis (Moore, 1870), corhiensis (Moore, 1870), and rockwoodensis (Etheridge, 1892). The first four species are characteristically Aptian (Day, 1964; Vine and Day, 1965; Ludbrook, 1966), although barklyi may range down into the Neocomian in the Wrotham Park Sandstone, which Woods (1961) places in the Neocomian. M. rockwoodensis is an Albian species (Vine and Day, 1965; Ludbrook, 1966).

Skwarko (1966) has recently described four species of Maccoyella, three new, from the Lower Cretaceous of the Northern Territory, Australia. His succession of species is as follows: Unit 6 (Aptian) M. cf. corhiensis (Moore). Unit 4 (late Neocomian) M. cf. corhiensis and M. transitoria Skwarko. Unit 2 (late Neocomian) M. cf. corhiensis, M. mullamanensis Skwarko, M. neocomiana Skwarko, and ?M. transitoria Skwarko.

M. mullamanensis and M. neocomiana occur with M. cf. corhiensis at different localities in his Unit 2, but apparently not at the same locality or at the same stratigraphic horizon.

Because of uncertainties in the systematic status of Skwarko’s species (see below), their relationships to other Australian species, and their stratigraphic position the evidence for a Neocomian age for his Units 2 and 4 is slender. The assemblages contain many new species and the stratigraphic framework is uncertain, being based on the position, inland from the coast, of scattered and isolated sections lacking persistent marker horizons. Nor is the fossil evidence convincing, being based largely on comparisons between infaunal trigoniids. The presence in Skwarko’s Units 2 and 4 of species either identical with or very similar to species characteristic of the Aptian-Albian of the Great Artesian Basin, e.g., Fissilunula clarkei (Moore), Thracia primula Hudleston, M. cf. corhiensis, Nototrigonia cf. cinctuta (Etheridge), Panopea cf. sulcata Etheridge, and Tatella cf. aptiana Whitehouse in the writer’s opinion indicate an Aptian, rather than Neocomian age.

Brunnschweiler’s (1954) report of an Upper Jurassic species of Maccoyella led Waterhouse (1959) to consider a downward extension of the range of the genus. Brunnschweiler (1960) subsequently reclassified the specimens in Meleagrinella (Speden, 1968). Consequently, the known range of Maccoyella in Australia is PNeocomian, Aptian-Albian. The Aorangi Range species probably falls somewhere within this age range.

Although the relationships of the Aorangi Range Maccoyella are too uncertain to allow a more exact age than Lower Cretaceous, the stratigraphic range of the few specimens of Maccoyella known at Koranga suggests that the Aorangi Range fossils may be pre-Motuan (pre-Upper Albian) (Vella, 1961). At Koranga M. magnata Marwick occurs in the Korangan (Aptian), and recently the writer has identified a steinkem of a left valve of Maccoyella sp. indet. (NZGS-TM4051)

in a collection (NB7/559, G 59761) from the overlying lower Urutawan Stage (Lower Albian).

Genus Nuculana Link, 1807 Nuculana (5.1.) sp. PI. 1, figs. 1-3.

Description : Small, inequivalve, inequilateral, moderately inflated, slightly rostrate. Umbones moderately projecting, at about anterior one-third of length, prosogyrous. Escutcheon distinct, slightly to moderately sunken, not bordered externally by a sharp keel. Ornament unknown, apparently weak.

Resilifer small, deeply sunken, not projecting ventrally below hinge line, interrupts the teeth beneath umbones. Dentition taxodont, with about 10 anterior and 13-15 posterior teeth. Musculation and shell structure unknown.

Types: Hypotypes. VMBS4, a left-valve steinkern, VMBS6, a left-valve steinkern, and VMBS7, external mould of the dorsal part of a right valve; all from loc. V 2086.

Material : Six poorly preserved steinkerns and several fragments from Putangirua Stream, locality V 2086.

Discussion and Comparison: Because of the paucity of specimens and their poor preservation in the coarse-grained matrices of the Whatarangi Formation many of the diagnostic features of nuculanid bivalves, especially the form of the rostrum, musculation, and ornament, are unknown. The shape, inflation, and form and prominence of the umbones favour classification in Portlandia Morch, 1857, type species Nucula arctica Gray (Opinion 769, Bull. Zool. Nomen., v. 23, p. 33), or Jupiteria Bellardi, 1875, type species Nucula concava Bronn. The form of the escutcheon and apparent lack of a ventral sinuosity on the rostrum favour classification in Jupiteria. However, a flattening of the postero-ventral surface on VMBS6 (PI. 1, fig. 2) possibly suggests the presence of a small ventral sinuosity and so makes classification in Jupiteria uncertain.

Better preserved, very similarly shaped, but larger specimens which are congeneric with and possibly conspecific with the Putangirua Stream specimens are known from Waiotahi River, N7B/526 (G 59594). These specimens come from weathered sandstones which overlie the silty mudstones containing Maccoyella incurvata Waterhouse (Waterhouse, 1959; Speden, 1968). Unfortunately the age of these sediments is not known precisely, but it is probably either Korangan Stage or, more likely, lower Clarence Series, i.e., Aptian-Albian.

Genus Maccoyella Etheridge, 1892 Maccoyella sp. PI. 1, figs. 4—13, 15, 17.

Diagnostic Characters: Large number (14-27) of primary, secondary and tertiary radial costae on the first five millimetres of shell height from tip of umbone. Radial ornament present on the posterior wing.

Description: Small, length of specimens 2.8 to B.omm, inequilateral, inequivalve. Umbones at about one-third of the length of the disc of the shell.

Left valve larger than the right valve, moderately inflated, with a small anterior wing and a large posterior wing, the postero-dorsal margin of which is usually rounded but sometimes attenuated to a small point. Umbone inflated, relatively narrow, projects slightly above the dorsal margin. Shell ornamented by 14 to 27 strong narrow radial ridges, initially costate but rapidly becoming plicate on the main disc of the shell while remaining costate on the posterior wing. Costae weaker on the posterior wing which usually has a strong costa close to the postero-dorsal margin. Radial plicae triangular in cross-section and slightly narrower than the interspaces. Nine to 10 primary radials appear at less than o.smm from the tip of the umbone. Secondary and rare tertiary radials appear by intercalation at 0.8 to 2.omm and 4 to smm respectively from the tip of the umbone. Secondary costae normally rapidly become

as strong as the primary, but remain weaker for the height of the valve on a few specimens. Fine concentric striae, 3 to 4 per millimetre, cross the interspaces and form small nodes and spines on the radial plicae/costae. At major growth lamellae these spines are fistulose.

Right valve suboval, convex, smaller and less inflated than the left valve. Byssal ear relatively large, separated from the disc of the shell by a narrow and deep byssal notch. Apparently lacking radial costae (see discussion below).

Ligament area and hinges of each valve similar to those of M. incur vat a Waterhouse as described by Waterhouse (1959) and Speden (1968).

Right valve with a large subcircular postero-ventral adductor muscle impression and a small oval deeply impressed pit in the umbonal cavity, the two scars joined by a pallial line of discontinuous linear scars. Musculation of left valve unknown.

Shell structure and composition unknown. Hypotypes : VMBSS, 857-867, all from V 2086, Putangirua Stream, in boulders, Lower Cretaceous.

Measurements : Corrosion accompanying the burial of the specimens in coarse pebbly grits has resulted in most of the specimens being incomplete around the ventral margin and the postero-dorsal wing. Consequently, the measurements given in Table I are approximate only.

Discussion: The coarseness of the matrix in which the majority of specimens occur has obscured fine detail and has made it difficult to decide whether the right valves truly lack radial costae. A few specimens enclosed in finer sand lenses suggest that the valves are genuinely smooth, but this is uncertain.

Material: About seventy almost complete single valves and many fragments. Occurrence; As specimens in boulders at two localities; Putangirua Stream (N165/1010) and Te Ika Pakeke Stream (N165/1011).

Comparisons: Two factors affect comparison with the Australian species of Maccoyella. First, the morphology and relationships of the Australian species are poorly known, especially with regard to variation in the number of radial plicae and the point of entry of the orders of plicae. Secondly, the Aorangi Range Maccoyella occurs in coarse-grained sediments obviously deposited in a high-energy environment. Consequently the small size of the specimens possibly indicates derivation from a population composed purely of juveniles, or from a “ stunted ” population, so that the true shape and ornament of normal-sized adults of the species are uncertain.

The number of orders of radial plicae, and the range of incoming of plicae within an order are important criteria for the identification of the species of Maccoyella. Unless each order is clearly demarcated they may be difficult to recognise and the comparison of species may be complicated, particularly if what are called first-order plicae by one worker include two or more orders of another worker. For example, I recognise on the Aorangi specimens second-order plicae entering at 0.8 to 2mm radius from the tip of the umbone and third-order at greater than 4mm. But a large number of specimens might show these two groups to belong to a class of second-order plicae entering between 0.8 and, say, 8-10 mm, with true third-order plicae entering at, say, greater than 15 to 20mm.

On the main disc of specimens available to me the second order plicae appear at about the same distance from the tip of the umbone over a range of no more than 1 to 2mm. On the posterior flank the plicae generally enter at 1 to 3mm later. The appearance of third and fourth order plicae on individual species occurs over a large range, perhaps as much as smm.

Mr R. W. Day, Geology Department, Australian National University, is at present revising the systematics of the Australian species of Maccoyella, including the uncertainty over the concept of M. corhiensis Moore (Skwarko, 1966, p. 76). Mr Day’s study should facilitate identification of the New Zealand species. In the following the Aorangi Range Maccoyella is compared only with the better known

Australian species. My concept of corhiensis as a moderate-sized species with about 25 to 35 radial plicae and costae on each valve (cf. Speden, 1968) is based on specimens (NZGS-WM9046-9049, 9250) identified by and sent to me by Mr Day.

1. Size. If the Aorangi specimens represent adults, which is uncertain, their small size clearly separates them from all other described species, which reach at least twice their maximum size.

2. Shape. In shape, inflation, and incurved form of the left-valve umbone the Aorangi specimens resemble M. corhiensis (Moore) (PI. 1, fig. 20), and small specimens of the flat M. harklyi (Moore) (PL 1, fig. 19) and the gryphaeoid M. incurvata Waterhouse. While juveniles may closely resemble each other in shape, ontogenetic changes with growth, especially in the degree of gryphaeation, may produce distinctively shaped adults.

3. Spinosity. The presence of small tubular spines at the point of intersection of most concentric striae and the radial ornament gives well-preserved Aorangi specimens a distinctive ornament and clearly distinguishes them from incurvata, which has solid spines only where strong growth-pause laminae cross the radial plicae. Maccoyella harklyi (Etheridge, 1892, p. 455), reflecta (Etheridge, 1892, p. 457; 1902, p. 19), neocomiana Skwarko and transitoria Skwarko have tubular spines, although these also tend to occur on prominent growth laminae. M. corhiensis apparently has no spines.

The presence of tubular spines is apparently related to the number and strength of concentric striae. Species with a few strong striae, such as harklyi and reflecta which have two to four per millimetre, possess tubular spines, but species with numerous fine concentric striae, such as corhiensis and incurvata which have 9 to 16 per millimetre, lack tubular spines.

4. Ornament of the right valve. If the Aorangi specimens lack radial costae they clearly belong to a new species. If radials are present then they must be few in number and warrant inclusion of the Aorangi specimens in the group of rockwoodensis and incurvata, which have a few widely spaced radials (up to about 14 and 9 respectively), and not in the group of harklyi and reflecta, which have more than 50 radials, or in corhiensis which has about 25 to 35 radials.

5. Ornament of the left valve. Because of the small size of the Aorangi specimens the most important criteria for comparison with other species is the number and point of appearance of radial costae and plicae on the left valve. Data for the better known species of Maccoyella are given in Table 11. The data are based on specimens held in the collections of the New Zealand Geological Survey, with some additional information for harklyi from literature. Counts and measurements were made on the first smm height from the tip of the umbone.

The total number of radials on the first smm of shell height clearly distinguishes the Aorangi specimens from M. incurvata, M. cf, corhiensis (Moore) of Skwarko, M. mullamanensis, and M. neocomiana. In the number of primary costae in smm the Aorangi specimens overlap most species, but appear generally to have more than harklyi and fewer than corhiensis. Available specimens of harklyi have more than 12 primary radials. On the Aorangi specimens the secondary radials enter at less than 2mm, while on harklyi and corhiensis they appear after 3mm and are not nearly as numerous. Tertiary radials enter at less than smm from the tip of the umbone on the Aorangi species, but on corhiensis, harklyi, and reflecta they appear after 12mm on all specimens on which they occur.

The umbone of the holotype of transitoria Skwarko (1966, pi. 6, fig. 21) is too poorly preserved to be certain of its pattern of entry of radials. It seems that primaries and secondaries appear on the first 5 to Bmm of shell height and tertiaries

at about 15mm. There is a superficial resemblance to some specimens from the Aorangi Range.

The Aorangi specimens also differ from the Australian species in the presence of two to four radials on the posterior wing (PI. 1, Fig. 10), commonly with one strong costa close to the dorsal margin. Descriptions of the Australian species stress the absence of radial costae from the posterior wing, and none are evident on specimens available to me. According to R. W. Day (letter April 17, 1967) radial ornament is apparently absent on the posterior ears of M. corbiensis and is faint on M. barklyi. Etheridge (1892, p. 448) reports one or two radials on the posterior wing of the relatively poorly known rockwoodensis.

To sum up: the Aorangi Range specimens show a wide range of variation in number and pattern of radial costae and plicae on the left valve. Some, those lacking numerous secondary and tertiary radials, resemble individual valves of barklyi, corbiensis, and the holotype of transitoria Skwarko, but these species differ in having few secondary and no tertiary radials on the first smm of shell growth. The radials on the Aorangi Range specimens are narrower and more projecting than those on corbiensis, which either lacks or has very small spines, and lacks radials on the posterior wing.

The Aorangi Range specimens are here classed as Maccoyella sp. Most of them can be distinguished from typical specimens of Australian species available to me. Open nomenclature has been adopted because the Aorangi Range specimens may not have reached adult size, because the ornament of their right valves is uncertain, because they vary greatly in radial ornament and the corresponding variation in the Australian species is unknown, and because they closely resemble the umbonal regions of specimens of barklyi and corbiensis (as here interpreted).

The possibility that the Aorangi specimens may be juveniles of M. magnata Marwick has been considered, but the only specimen has a damaged, worn umbone and an incomplete postero-dorsal margin, which prevent comparison.

Genus Pseudolimea Arkell, in Douglas and Arkell, 1932 Cox (1944, p. 75) elevated Arkell’s subgenus Pseudolimea to generic status. Pseudolimea sp. PI. 1, Figs. 14, 18.

Description: Approximate measurements of the left valve are: length Bmm, height B.smm, half width 3.5 mm, anterior length 4mm, length of dorsal margin 2.6 mm, and anterior length of dorsal margin I.lmm. Shape typical of the genus with a narrow beak projecting above a small triangular cardinal area. Posterior wing slightly larger than anterior, both ornamented by three to four short, weak costae which are concave dorsally. Main disc of shell with 12 V-shaped radial plicae with steep sides and sharp crests. Interspaces broader than the plicae, with a concave floor and one weak central costa, and crossed by fine concentric striae. Hinge with three to four strong teeth on each side of the cardinal area (PI. 1, fig. 18).

Musculation and shell structure unknown. Material: An external mould of a broken left valve (VMB7O) and several small fragments.

Comparison : A distinctive, undescribed species of Pseudolimea in the Korangan and Urutawan stage sequences of the Matawai District (Wellman, 1959: 147) generally develops its distinctive multicostate plicae, bearing spinose secondary costae, at distances of 6—lomm from the beak. Although similar to the Matawai species in shape and number of radial plicae the Putangirua specimen appears to have simple plicae. However, it is too poorly preserved and too small to permit valid comparisons.

Phylum ANNELIDA Lamarck, 1809

Genus Rotularia Defrance, 1827 Rotularia sp. PI. 1, Fig. 16. Description : Tube tightly coiled in a low helicoid, dextral spiral. In cross-section the tube has an upper keel, forming about one-quarter of the height, followed below by a strong round-

floored depression and then by a rounded keel which comprises about two-thirds of the height of the tube. Three shallow U-shaped spiral grooves subdivide the basal keel into four roundcrested spiral carinae (Fig. 1). Base of tube with a shallow to prominent and deep spiral groove. Straight tubular fragments suggest that the apertural part of the last whorl is free from the spiral part of the whorl.

Material: Two incomplete specimens, each part of a whorl showing ornament and cross-section of the tube, and several fragments. Poor preservation prevents the study of fine detail.

Discussion: Stevens (1967) has reviewed the Rotularia from the Jurassic and Cretaceous of New Zealand and compared them to overseas species.

None of the New Zealand specimens possesses four carinae on the keel, and no overseas species are similar in shape and ornament of the whorl. However, the Putangirua Stream specimens are too incomplete, too poorly preserved, and too few for firm comparisons or for the proposal of a new species.

Acknowledgments

I am indebted to Mr T. E. Bates, Victoria University of Wellington, now with the International Nickel Southern Exploration Ltd., Kalgoorlie, Western Australia, for the opportunity to examine and describe his fossils from the Whatarangi Formation. Professors Paul Vella and H. W. Wellman, Victoria University of Wellington, kindly facilitated description of the collections and also read and criticised the manuscript. Mr Stephen Eagar, of the University, assisted the curation of the specimens. The collections were greatly augmented by the efforts of Professor Wellman, Dr A. J. Wright, Dr R. A. Henderson, and Mr M. R. Johnston, all of Victoria University of Wellington, who accompanied Mr Bates and myself in the field.

Mr R. W. Day, Geology Department, Australian National University, Canberra, and Dr S. K. Skwarko, Bureau of Mineral Resources, Canberra, greatly aided the description of the Maccoyella species by the exchange of specimens, literature, and correspondence. Mr Day, Dr G. A. Fleming, and Dr G. R. Stevens, New Zealand Geological Survey, Lower Hutt, kindly read manuscripts and offered valued advice.

References

Arkell, W. J., in Douglas, J. A.; Arkell, W. J., 1932. The stratigraphical distribution of the Cornbrash: 2. The north-eastern area. Q. Jl geol. Soc. Land. 88: 112-170.

Bates, T. E., 1968. The Whatarangi Formation (Lower Cretaceous), Aorangi Range, Wairarapa, New Zealand. Trans. R. Soc. N.Z., Geol. 6: 139-42.

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Cox, L. R., 1944. On Pseudolimea Arkell. Proc. malac. Soc. Lond. 26: 74-88. Day, R. W., 1964. Stratigraphy of the Roma-Wallumbilla area. Geol. Surv. Queensland Publ. 38.

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Skwarko, S. K., 1966. Cretaceous stratigraphy and palaeontology of the Northern Territory. Bull. Bur. min. Resour. Aust. 73.

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Vine, R. R.; Day, R. W., 1965. Nomenclature of the Rolling Downs Group, Northern Eromanga Basin, Queensland. Queensland Gov. Mining /., Sept., 1965, pp. 2-6.

Waterhouse, J. 8., 1959. A new species of Maccoyella from Raukumara Peninsula, with a revision of M. magnata Marwick. N.Z. Jl Geol. Geophys. 2: 489-500.

Wellman, H. W., 1959. Divisions of the New Zealand Cretaceous. Trans. R. Soc. N.Z. 87: 99-163.

Woods, J. T., 1961. Mesozoic and Cainozoic sediments of the Wrotham Park area. Geol. Surv. Queensland Publ. 304.

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Dr lan G. Speden, New Zealand Geological Survey, P.O. Box 30368, Lower Hutt, New Zealand.

* Species described under Systematic Descriptions.

+ Plus counts made on illustrations in Etheridge, 1892 and 1902.

* Irregularly near ventral margin of shell, from about 15-30 mm. from tip of umbone.

t See text for discussion of the number of radials on corbiensis.

Note: values given for ranges are for the sample and not for individual specimens.

Half Anterior Teeth Valve Length Height Width Length Anterior Posterior left, VM854 6.5 4.2 1.3 2.5 t. 10 c. 13 left, VM856 6.2 4.5 1.7 2.5 c. 10 c. 15

Measurements (in millimetres, approximate only).

Length Height width Half Anterior length Length of byssal ear Length of anterior wing Anterior length Length of byssal ear Length of anterior wing LV RV LV RV LV RV LV RV RV LV 8.0 9.6 3.1 3.8 1.5 5.8 5.8 2.1 2.3 1.8 6.6 5.0 2.3 3.0 2.0 3.5 3.3 1.4 1.4 0.8 7.0 6.6 2.8 3.0 — 6.2 6.3 2.6 • 1.9 4.0 4.2 2.0 — 1.5 3.5 3.3 1.4 1.4 0.8 2.8 2.6 0.5 1.2 0.8 4.8 4.0 0.9 1.6 — 2.6 2.6 0.6 1.1 0.8 7.2 7.3 2.5 2.9 — 6.7 7.4 1.4 2.9 1.2 6.4 c.5.4 — 2.8 — 6.3 5.1 1.2 2.5 — 3.6 3.2 0.8 1.5 0.6 5.0 4.8 — 2.3 1.1 LVvalve right RV

Table I.—Measurements (in millimetres) of Maccoyella sp. from the Whatarangi Formation, Aorangi Range.

LEFT VALVE SPECIES Number of specimens of costae 5 mm. of primary costae 5 of entry mm. of secondary costae 5 of entry mm. Tertiary costae 5 of entry mm. ofNo. costae 5 of entry mm. incurvata 8 6-9 6-9 1-3 1-2 4-15 0 * 6-10 1-5-2 Aorangi specimens 6 14-27 9-10 <0-5 4-10 0-8-2 1-7 >4 0? — t 7 16-21 12-16 <0-5-1 0-7 3-11 0 * >14 <2-5 barklyi 2 10-15 9-14 <0-5-1 1-4 4-15 0 * >30 <2-5 cf. M. 1966 Skwarko, 7 9-13 9-13 <1 — >7 — >15 10 ?

Table ll.—Comparison of the number of, and point of entry of, radial plicae and costae of some species of Maccoyella.