WATSON : ANATOMY OF OCHTHEPHILA. 293 



group is closely allied to that of the Western Palsearctic Region ; but 

 it has sometimes been thought that when their anatomy came to be 

 examined it would be found that the peculiar groups of snails found 

 on these Atlantic islands might prove to be relatively primitive forms 

 that had survived there owing to their isolation, and that these 

 groups might be more nearly related to one another than to the 

 genera which ara now dominant on the continent of Europe. This 

 view is not supported by our present knowledge of the anatomy of 

 these snails. OchthepMla turricula is rather prinaitive in its ureter 

 and in its radula, but not more so than many common European 

 Helicids ; and it is by no means primitive in its nervous system and 

 reproductive organs. On the whole, therefore, OchthepMla does not 

 seem to be any more primitive than the majority of European 

 genera. And if we compare the anatomy of Ochthejohila with what 

 is known about the internal organs of the other groups found in 

 Madeira, we find far greater difierences than those that separate 

 it from Helicella. Judging from the accounts of Pilsbry ^ and 

 Cockerell,^ Leptaxis difiers from Ochthephila, in that the right ocular 

 retractor passes between the penis and the vagina, there is a slender 

 flagellum, a large dart-sac containing a dart, and two clusters of 

 mucous glands, and the receptaculum seminis and jaw are both 

 somewhat peculiar. Cockerell's description and figures of the 

 anatomy of Helix (Idiomela) suhpUcata (Sow.) ^ show that, while 

 this group differs from Leptaxis in certain features, it is still more 

 unlike Ochthephila, the jaw, radula, and reproductive organs being 

 all of the type characteristic of the genus Helix. Thus it is probable 

 that the different groups of snails found on the Madeira Islands are 

 more nearly related to different genera living on the continent of 

 Europe than to one another ; and that at the date when the ancestors 

 of the snails now living in the Madeira group became isolated the 

 different types of anatomy found in the Western Palaearctic Helicids 

 had already been evolved. 



EXPLANATION OF PLATE VI. 

 Ochthephila turricula (Lowe) ; Cima I., Porto Santo. 



FIG. 



1.— Shell. X 4. 



2. — Mantle-edge, showing body-lobes. X 9. 



3. — Retractor muscles. X about 7-5. 



4. — Central nervous system. X 15. 



5. — Reproductive organs. X 1.1. 



6. — Longitudinal section of the junction of the epiphallus and penis, showing 



the penis-papilla. X 15. 

 7. — Jaw. X 35. 



8. — Representative teeth from the radula. X 450. 

 9. — Alimentary canal and salivary glands, the liver having been removed. 



X 7. 

 10. — Heart, kidney, and ureter, seen from the outer side. X 9. 



1 Man. Conch., ser. ii, vol. ix, 1895, p. 292, frontispiece, figs. 8, 9, pi. Ixvii, 

 figs. 19, 20. 



2 Proc. Malac. Soc, vol. xiv, 1921, p. 194, figs. 2, 3 (p. 193). 



3 Ibid., p. 192, figs. 1, la (p. 193). 



