murdoch : anatomy of ashmunella. 83 



Internal Anatomy. 



The dentition gives the formula 26 — i — 26 or ii- — 15 — i — 15 — 1 1, 

 in transverse, nearly straight rows ; the form of the teeth is very 

 similar to that of the preceding species. The jaw is strong, arcuate, 

 with fourteen or fifteen ribs which denticulate the margins, those in 

 the middle area are strongly developed, but towards the ends they 

 become weak and indistinct. 



The Generative Organs (PI. vii, fig. 8). — The penis is of medium 

 length, slightly contracted in the middle, with the posterior portion 

 less robust ; continuing as the epiphallus, which is about three times 

 the length of the penis, the vas deferens opens into it a little below 

 the apex. The retractor muscle is inserted in the lower third of the 

 epiphallus, and differs from that in the preceding species in that it 

 has but a single attachment. The internal wall of the penis exhibits 

 several fleshy plications, which are continued into the epiphallus and 

 are delicately convoluted. The receptaculum seminis forms a narrow 

 tube shortly after branching from the free-oviduct, with an expanded 

 apical portion. It extends almost to the base of the albumen gland. 

 Internally the walls of the lower portion are studded with small 

 granules, while those of the free-oviduct have the usual plications. 

 Other organs are similar to those of the preceding species. 



In addition to the shell characters, the external features of the 

 animal, the jaw and dentition are the same as Polygyra ; on the other 

 hand the generative organs resemble the Epiphallogonous Helices. 

 Pilsbry and Cockerell assign Aslinmnella to the Belogona group, 

 regarding it as having lost by degeneration the dart-sac and associated 

 mucous glands. In cases such as this it would be of special value 

 could we determine the group to which it is allied, by organs totally 

 uncorrelated with the generative organs. Pilsbry' states that the 

 pallial organs supply facts for phylogenetic research not less in import- 

 ance than those derived from the generative organs, and supports the 

 statement with comparative measurements of a number of genera, 

 all of which are included in the Epiphallogona. The characteristic 

 feature in the above group is the long, ribbon-like kidney, which is 

 from four to ten times the length of the pericardium, and extends to 

 as much as three-fourths of the total length of the lung. A. pseudo- 

 donta is seen to differ considerably from the above, and apparently 

 does not belong to the group, but a knowledge of the Belogona 

 Euadenia is required before accepting this evidence as conclusive. 



7 Proc. M.ilac. Soc. Lond., 1901, vol. iv, p. 161. 



