WATSON : ANATOMY OP OOHTHEFHILA. 291 



riglit of the right ocular retractor, in the well-developed epiphallus 

 and short flagellum, in the position of the degenerate mucous glands, 

 and in the unb ranched receptacular duct of moderate length. More- 

 over, the degeneration of the dart apparatus occurs also in these 

 genera, especially in Theba, culminating in the entire absence of 

 these organs in Ashfordia granulata (Alder). The jaw of Ochthephila 

 turricula is intermediate in type between that found in Theba, in 

 which there are usually a rather larger number of ribs, and that found 

 in Helicella, in which the number of ribs is generally smaller.^ The 

 radula is also of the same type, although in the larger or more 

 specialized species of these genera the endocone often becomes com- 

 pletely united with the mesocone in the marginal, as well as in the 

 lateral teeth. Even in the shell some species of Ochthejphila, such as 

 0. michaudii (Dh.), closely resemble Helicella, although this cannot 

 be said of the species here described. Almost the only anatomical 

 character that seems to separate 0. turricula from Helicella and the 

 other European Helicids is the very broad and obtuse form of the 

 flagellum, and it remains to be seen whether this feature is a constant 

 character of the genus ; Cockerell states that in 0. consors (Lowe) 

 " the stout flagellum ends in a nipple-like papilla",^ but he gives no 

 figure of it . 



Thus it would seem that the affinities of the genus Ochthephila are 

 with Helicella and Theba, genera which are usually regarded as rather 

 closely allied to each other. Hesse, however, considers that Theba 

 is related to Hygromia rather than to Helicella, notwithstanding the 

 diiierent position of the right ocular retractor, chiefly because 

 Theba more nearly resembles Hygromia in the coloration of the shell 

 and mantle.^ But this character does not seem to be of much 

 importance, being largely dependent on the environment. We find, 

 moreover, that in some species of both Hygromia and Theba the shell 

 is semi-opaque with brown bands, and it is not unlikely that in the 

 common ancestor of all the genera the shell was not more con- 

 spicuously striped than in these species. If this be the case, it would 



^ According to Pilsbry (op. cit., p. 238) and Cockerell {Proc. Malac. Soc, 

 vol. xiv, 1921, p. 195) in Ochthephila (Hystricella) bicarinata (Sow.) and 

 0. (Discula) polymorpha var. discina (Lowe) the jaw has but ten ribs, while 

 in 0. {Plebecula) lurida (Lowe) it has only eight, being thus of the type found 

 in Helicella. On the other hand, Pilsbry states that the jaw of 0. {Gaseolus) 

 abjecta (Lowe) has no ribs at all. 



2 Journ. of Conch., vol. xvi, 1922, p. 311. 



* Archiv fur Molluskenkunde, vol. liii, 1921, p. 56. Hesse also mentions 

 a possible difference between Theba and Helicella in the palhal lobes near 

 the respiratory opening ; but an examination of these lobes shows that they 

 are very similar in Hygromia, Theba, Helicella, and Ochthephila. 



It should be explained that in the present paper the names Hygromia 

 and Helicella are employed, in the way in which they are used by Pilsbry 

 and others, for the geilera of which H. cinctella, Drap. and H. itala, Lin. are 

 the respective types ; for I have given reasons elsewhere (Journ. of Conch., 

 vol. xvi, 1922, pp. 277, 279) for beheving that this usage is in accordance with 

 the International Rules of Zoological Nomenclature, notwithstanding recent 

 suggestions to the contrary. 



