278 PROCEEDINGS OF THE MALACOLOGIOAL SOCIETY. 



This objection, however, fails to take into consideration the fact 

 that in these relatively larger forms, such as Acanthinula aculeata, 

 the male organs, when present, are specially complicated and there- 

 fore presumably occupy more space. 



The Evidence op the Genital Organs in connexion with 

 THE Classification of the British Vertiginin^. 



A detailed study of the entire Anatomy of a larger number of 

 specimens will be necessary before we can form an adequate judgment 

 of the mutual affinities of these small species. Nevertheless, it is 

 worth noticing that if the species dealt with in this paper were to be 

 classified according to their genital organs alone, the result would 

 be somewhat as follows : — 



(1) Penis (when present) long, containing glandular tissue ; vas 

 deferens very long ; receptacular duct also very long. — Vertigo 

 moulinsiana (Dupuy), F. untivertigo (Drap.), F. jpygmom (Drap.), 

 F. alpestris. Alder, and almost certainly F. suhsttiata (Jeffr.) and F. 

 pusiUa, Miill., although in the last two species the form of the penis, 

 if that organ ever occurs, is not yet known. 



(2) Penis (when present) rather small, without glandular tissue; 

 vas deferens not exceptionally long ; receptacular duct of moderate 

 length. 



[a) Glandular part of genital duct composed of three portions 

 difiiering widely in structure ; hermaphrodite gland divided into 

 two parts. — Truncatellina 6ntonwica, Pilsbry. 



(6) Glandular part of genital duct composed of two main 



portions differing slightly in structure ; hermaphrodite gland not 



divided into two parts. — Columella edentula (Drap.). 



It will be seen that this classification agrees remarkably well 



with one founded solely on the characters of the shell. If, however, 



the radula were also to be taken into consideration, F. moulinsiana 



would probably have to be placed slightly apart from the other 



British species of Vertigo, for the radula of this species is peculiar in 



that the lateral and marginal teeth are all approximately fH-shaped, 



and scarcely differ from one another .^ 



The reproductive system of Truncatellina briiannica differs in 

 several respects from that found in the other species examined, as 

 may be seen from the description given above (on p. 274). It is thus 

 evident that this species is rightly placed in a distinct genus. Its 

 radula may be described as intermediate in character between the 

 type found in Vertigo jpygmcBa and its allies, and that found in the 

 genus Columella ; but it more nearly resembles the former type than 

 the latter. In this minute species there are not more than eleven 

 teeth on each side of the central in each transverse row. 



1 See Tomlin and Bowell, Journ. of Conch., vol. xii, 1909, pp. 215, 298, 

 pi. V. 



