Research Note Further Notes on the Affinities of Arhynchobatis asperrimus Waite with Other Rajoids, and Data on a Fourth Specimen By J. A. F. Garrick [Received by the Editor, March 25, 1957.] Arhynchobatis asperrimus is a unique rajoid in that it possesses only one dorsal fin, in addition to a large and complete caudal fin. It is known only from three previous female specimens, all from New Zealand waters, though a dried example of a fourth specimen, also from New Zealand, was reported by Archey (private communication) but is no longer available. Some uncertainty as to the status of A. asperrimus in recent accounts of the Rajoidea by Bigelow and Schroeder (1953, 1954) indicates a need for further information on several morphological features of this species Moreover, in view of the characters put forward in these accounts by Bigelow and Schroeder as of primary importance in rajoid classification, a review of the affinities of A. asperrimus on this basis is timely. The original account of A. asperrimus, by Waite (1909), based on a single female specimen 640 mm long and trawled from 66–94 fathoms in the Bay of Plenty by the New Zealand Government Trawling Expedition of 1907, and for which Waite established the genus Arhynchobatis, was, until 1954, the only information available on it. The apparent lack of definition of certain morphological features in this account resulted in the species receiving various systematic placings by later authors, even though Waite recognised it as belonging to the Rajidae and having affinities with Psammobatis. Thus Garman (1913) placed it in the Discobatidae, and Fowler (1941), and Richardson & Garrick (1953) in the Platyrhinidae. Bigelow & Schroeder (1953, 1954) recognised it as belonging to a distinct family, Arhynchobatidae, in the Rajoidea. The capture of two further specimens, both females, and 750 mm and 695 mm long respectively, from 50–60 fathoms off the east coast of the North Island in September, 1953, resulted in an extended account of the species, including a description of the endoskeleton, by Garrick (1954), where it is shown that not only is it definitely a member of the Rajoidea, but apart from the lack of a second dorsal fin and the presence of the complete caudal, the species differs from species of the genus Raja only in the short rostral cartilage which protrudes little anterior to the nasal capsules. The reasons for assigning the species to the Rajoidea rather than to the Platyrhinidae need not be repeated here. It is sufficient to say that the external morphological features, together with the nature of the pelvic bar, in which the transverse element is almost straight and bears prominent, pointed, lateral prepelvic processes, conform to the Rajoidea and suggest no other suborder. A further feature of the Rajoidea not previously recorded for Arhynchobatis but discussed by Bigelow & Schroeder (1954, p. 3) as a means of separating the members of this suborder from the Myliobatoidea, is the persistence of vestiges of the embryonic gill-filaments on the anterior wall of the spiracle; this feature can now be confirmed for A. asperrimus. The lack of the second dorsal fin, coupled with the presence of a complete caudal fin in Arhynchobatis, are unique features for the Rajoidea, and hence there can be no controversy on the distinction of Arhynchobatis. The majority of the Rajoidea have two dorsal fins and an incomplete caudal, as in the family Rajidae, while the few others lack a dorsal fin but have a complete caudal and are distributed on other characters between the two remaining families, Anacanthobatidae and Pseudorajidae. The short rostral cartilage, which in Arhynchobatis reaches very much less than half the distance from the neurocranium to the tip of the snout, is a character shared by genera in both the Rajidae and Pseudorajidae. Thus in the Rajidae, Psammobatis and Sympterygia either lack rostral cartilages—the anterior face of the neurocranium being straight or slightly concave—or have them barely produced, while Breviraja has a longer rostral cartilage though it fails to