Art. XVI.—On the Anatomy of Paryphanta fumosa, Tenison-Woods.

Transactions and Proceedings of the Royal Society of New Zealand, Volume 36, 1903, Page 156

Art. XVI.—On the Anatomy of Paryphanta fumosa, Tenison-Woods. By R. Murdoch. [Read before the Wellington Philosophical Society, 17th December, 1903.] Plate VI. Vitrina fumosa, Ten.-Woods. Proc. Lin. Soc. N.S.W;, iii., p. 124, pl. xii., figs. 3, 3a. V. fumosa, Ten.-Woods. Petterd, Monograph, “Land Shells of Tasmania,” 1879, p. 51. To the kindness of Mr. Charles Hedley and Mr. W. F. Petterd I am indebted for an example of this rare species. The specimen under notiee-was-collected and identified by Mr. Petterd, the original discoverer of the species. It was gathered at Mount Farrell, north-west Tasmania, and is certainly one of the rarest members of the genus Paryphanta. The shell (figs. 1 and 2) is subglobose, imperforate, exceedingly thin, shining, of a dark-olive tint, and without sculpture. Whorls 3, rapidly increasing in size. The spire small, lightly convex, and scarcely elevated above the body-whorl. Proto-conch consists of about 1 ¾ whorls, lighter in colour and apparently devoid of sculpture. Sutures impressed. The lines of growth on the body-whorl are minute, somewhat irregular, and have a slightly crimped appearance at the suture. Aperture broadly ovate and slightly oblique to the axis of the shell. Columella short, curved, and very lightly expanded. Outer lip slightly projecting at the suture. The umbilical area slightly impressed. Alt., 10 mm.; lat., 13.5 mm. The shell, with the exception of the apical whorls, appears to consist almost completely of conchin, and in this respect it resembles certain of the New Zealand species—e.g., P. urnula, Pfr. The animal is, unfortunately, very much contracted, hard, and difficult to handle. It is black or blue-black in colour, somewhat lighter posteriorly. The rugæ on the sides of the body and neck are large, irregular in shape, and do not

appear to form regular rows, except some two or three on the neck. Behind-the-visceral mass there is a median dorsal line which does not extend to the full length of the tail; and the rugæ on this area are considerably smaller than on the anterior portion of the animal. The tentacles are completely retracted, and the labial projections, if any, are not distinguishable. On the external surface of the mantle, and close to its margin, is a lightly impressed line of a dark-blue colour, and on the under-side are small right and left lappets, the latter forming a narrow inconspicuous fold. The foot is of a sepia colour around the margins, shading to lighter in the middle area; except in colour there is no indication of it being divided into median and lateral areas. It is thrown into several transverse prominent folds, and its whole area has the appearance of being minutely transversely and longitudinally grooved. This rugose aspect is doubtless largely due to its contracted condition. The buccal mass (fig. 3) is large, and very similar to the corresponding organ in other members of the genus; but in the form of attachment of the retractor muscle it differs from any that have come under my notice. The muscle is completely attached to the posterio-ventral side of the buccal mass; it extends from the posterior and forward to the flexure, as shown in the figure. The muscle forms, as it were, a double cushion (fig. 4), attached on the inner margins and anterior areas: In P. hochstetteri, Pfr., and P. busbyi, Gray, the retractor muscle almost envelops the curved-down posterior end of the buccal mass. It is roughly in the form of a hollow cone, but the greater portion of the muscle certainly goes to the ventral side. In longitudinal section of the buccal mass it is found that the area of greatest muscular concentration is at the ventral flexure or immediately posterior to it. To this area are attached the enormously developed posterio-dorsal series of muscles, which proceed from the odontophoral cartilage and radular sac. It would thus appear that in fumosa the retractor muscle is more completely applied to the area where the greatest resistance is required. The radula has the formula 38-0-38, the rows of teeth forming an obtuse angle curved towards the margins. The teeth (fig. 5) are all aculeate. They increase in length to about the ninth; a few succeeding teeth are apparently without change, thence they very gradually decrease in length; the twenty-fifth to the twenty-seventh diminish somewhat more rapidly, and the last is reduced to about one-half of the length of the adjoining tooth. With the exception of the innermost tooth, all have practically the same diameter; thus the teeth towards the margins, and the centre also, are in proportion to their length more robust than the intermediate teeth.

The œsophagus enters the buccal cavity in the anterior third; it is a thin, narrow tube, without any distinctly marked crop. The stomach forms a small elongated sac surrounded by the liver; and the tract of the intestine is apparently similar to Helix. The salivary gland (fig. 6) partly envelops the œsophagus, and is situate on the posterior portion of the buccal mass; it consists of right and left lobes, the former being somewhat the smaller. The two lobes anteriorly are almost completely fused together; viewed from the ventral side the divisional line is seen to form a well-marked furrow on the posterior half of the gland, but on the anterior portion it is scarcely indicated, and the two parts cannot be separated without severing the tissue of the gland. There is but a single salivary duct, which proceeds from the median cleft on the anterior end of the gland and enters the buccal cavity on the right of the œsophagus and slightly posterior to it. Transverse sections taken at the point where the salivary duct becomes merged in the gland show that the ducts proceeding into the right and lesser lobe are somewhat more conspicuous than those to the left side. Neither of the lobes or glands appears to have suffered any loss of function. In the situation of the salivary duct it has the appearance of having changed from its normal position, and to some extent doubtless it has, but it is presumable that the anterior end of the gland is more perfectly fused and drawn together than in its normal condition; also, it is fairly conclusive proof that in a normal state the glands are functionally united. The condition of the salivary glands in Paryphanta is somewhat variable: thus, in P. hochstetteri they are functionally united, while in P. busbyi they are distinctly separate in function. In the former species the union of the glands is most apparent in the very young individuals. The right gland is much the smaller; its duct divides into two branches, either immediately before or as it enters the substance of the gland. One of these branches proceeds to the anterior portion of the left gland, where it divides into several lesser tubes; also, the cellular structure of glands is continuous in this area. In adult specimens the line of cleavage between the two glands is much more pronounced, but there is always some portion in which the glandular mass is continuous. The left salivary duct unites with its gland in a position considerably posterior to that of the right duct and gland. The pedal gland (fig. 7) opens anteriorly between the head and foot; it forms a long slender tube much folded and lying upon the floor of the body-cavity. Its posterior end is enlarged, partly imbedded in a shallow cavity in the muscles of the foot, and from its ventral side proceeds a small muscle which unites with the adjoining tissue.

Retractor muscles: The buccal-mass retractor is very large, almost equalling the pedal muscles. Both muscles coalesce towards their posterior extremity. The tentacle-retractors arise in separate bands from the posterior portion of the pedal muscle; they bifurcate towards their anterior ends and supply the retractors to the inferior tentacles. The right ocular-retractor passes between the branches of the genital system. The form and position of the muscles, with the exception of the attachment of the retractor with the buccal mass, agree perfectly with the New Zealand species—busbyi,* Trans. N.Z. Inst., vol. xxxv., pp. 258–62, pi. xxvii. urnula,† Proc. Malac. Soc.', London, 1903, vol. v., pt. iv., pp. 270–73. and hochstetteri.† Pallial region (fig. 8): The kidney is tongue-shaped, its anterior end having a somewhat truncated appearance; in length it is twice its breadth, about half the length of the lung, and about one-third longer than the pericardium. The ureter is a well-marked tube of medium width; it follows the margin of the kidney, and appears to open into the right posterior corner of the lung close to the rectum. The pericardium is in the usual position on the left side of the kidney. The great efferent pulmonary vein follows the margin of the ureter to a point almost in line with the right border of the kidney; thence proceeds forward towards the respiratory pore. There are 3 comparatively large pigmented efferent vessels on the cardiac side of the lung; also in front of the respiratory pore are several small pigmented vessels from both rectal and cardiac sides. On the rectal area of the lung are numerous small efferent and afferent vessels, but they are not pigmented, and it requires a very careful illumination to show any trace of them. On the cardiac side are several afferent vessels, two of which are comparatively large, and with pigmented margins. Generative organs (figs. 9 and 10): The atrium is very short. The penis forms a simple sac of medium length, with the retractor muscle inserted in the posterior end and attached distally to the diaphragm. Its internal wall has a prominent thickening, yellowish in colour and the surface covered with minute granules; it extends from the entrance of the vas deferens to almost the anterior termination of the penis. The vas deferens arises a little below the apex of the penis; it has a few slight convolutions, thence a slender uniform tube until immediately before its union with the oviduct, where it is enlarged, almost sac-like. The vagina is somewhat slender, and in length rather more than equals the penis. The recep-taculum seminis is in the form of a small elongated sac, situate close to the sacculated uterus, and when the organs

are in a natural position (fig. 9) it is completely enveloped by the sacculations. Its internal walls are richly plicated. The albumen gland very large, and the hermaphrodite duct densely convoluted. The right lobe of the liver, including the hermaphrodite gland, was torn off and remained in the shell when extracting the animal. The systematic position of fumosa has already received some attention. Ancey, in Journal de Conchology, xlix., p. 12, places it in Paryphanta, and refers to it as an interesting Antarctic species. Suter, in the same publication (p. 316), at once throws doubt on its pertinence to Paryphanta. To this Ancey replies (J. de C., li., p. 44) that until anatomical investigation disproves it the species may by shell characters fairly be assumed to be a Paryphanta. The most striking peculiarity in the anatomy of the several known species of Paryphanta is the marked difference in their genital organs. The difference is chiefly centred in the receptaculum seminis; the contour of this organ is so distinct in each species that, when added to the minor difference in other organs, it presents a type of genitalia unusually distinct amongst species of the same genus. P. busbyi can scarcely be compared with the other members, its genital organs are almost totally different; but this condition is probably due to degeneration. On the other hand, the general anatomy does not appear to present any important differences, except the form of attachment of the buccal-mass retractor in P. fumosa. This divergence from the typical form is an important feature, for as a rule the form and position of the principal muscles in a genus or family show a far smaller range of variation than organs such as the jaw, dentition, or genitalia; however, apart from this feature, the arrangement of the muscles, as previously stated, is identical with P. hochstetteri; also, there is a mass of evidence from totally diverse, uncorrellated organs which is quite in accord with Paryphanta. Explanation of Plate VI. Paryphanta fumosa, Ten.- Woods. Fig. 1. Shell. " 2. Shell. " 3. Buccal mass, &c. " 4. Buccal-mass retractor muscle, form of attachment. " 5. Teeth. " 6. Salivary gland, ventral side. " 7. Pedal gland. " 8. Pallial region. " 9. Generative organs. " 10. Generative organs.

Reference Letters. af. v. Afferent pulmonary veins. alb. g. Albumen gland. ef. v. Efferent pulmonary veins. h. d. Hermaphrodite duct. int Intestine. rc. Rectum. k. Kidney. l. Left salivary gland. œs. œsophagus. p. Penis. per. Pericardium. r. Right salivary gland. r. m. Retractor muscle. r. s. Receptaculum seminis. s. d. Salivary duct. s. g. Salivary gland: u. Ureter. v. d. Vas deferens.