BOYCOTT : ON VITBINA MAJOR. 125 



absence of the comb-like external serrations on the outer externals, 

 which, are simple aculeate teeth as in pyrenaica.^ These multi- 

 cuspidate outer externals seem to be constant in pellucida, and their 

 presence has been verified for the present inquiry in specimens from 

 Shetland, Hereford (three localities), Brecon, Kadnor, Surrey, 

 Herts (six localities), Cheshire, Sussex, and Glamorgan. As far as 

 I have been able to find, they occur in no other described European 

 Vitrina, though a similar type of tooth appears to be present in 

 the North American forms (alaskana, limpida), which are doubtfully 

 distinct from pellucida. In the Cusop snail the ectocones of the 

 inner ' externals are relatively much smaller than in pellucida, in 

 which the two cones are almost equal in size ; in pyrenaica the 

 ectocones are still smaller. 



The shell (Figs. 2 and 3) is not strikingly different from that of 

 pellucida ; the spire is flatter and the mouth rather longer, the 

 colour and texture identical. From pyrenaica it is as distinct as is 

 pellucida. 



It is evident, then, that the Cusop form is quite different from both 

 pellucida and pyrenaica. But it is more difficult to say what it is 

 than what it is not. The genital anatomy corresponds as well as 

 can be expected with Moquin-Tandon's description and figures ^ of 

 F. major, a widely spread French species ; his description of the 

 dilatation on the oviduct as " demi-cartilagineuse " is particularly 

 striking, for that is just what it looks and feels like under the lens 

 and needle. The shell does not correspond so well. He divides his 

 six species of Vitrina into two groups : (a) with the columellar lip 

 flattened (" bord columellaire aplati "), semilimax {= elongata), 

 diaphana, pyrenaica ; (b) columellar lip sharp, major ( = draparnaldi), 

 pellucida, anmdaris. The Cusop shell has a slight but definite border 

 stretching from the columella along the lower margin where the 

 edge of the shell is bent inwards, that is, it has in a small degree 

 what is a prominent shell character in pyrenaica. The specimens of 

 major in the British Museum all have a sharp edge without the 

 flattened border ; so has a specimen of major from the Ardennes, 

 which Mr. J. W. Taylor has been good enough to give me. But I 

 am not inclined to attach to this character (at any rate, when 

 slightly developed) the same importance that Moquin-Tandon 

 does. For I find that it is present in a few pellucida, noticeably 

 in those found with the new shell in Cusop Dingle, and plainly in 

 several Hertfordshire specimens ; Taylor ^ mentions the occasional 

 presence in pellucida of an " apertural film ", and Eckardt ^ figures 



^ For figures of pellucida see Taylor, Monograph, iii, 1906, p. 6, and of 

 pyrenaica the same, iii, 1914, p. 453 ; and Bowell, Irish Naturalist, xvii, 1908, 

 p. 94. 



^ Histoire Naturelle, vol. ii, 1855, p. 51, pi. vi, figs. 26, 27. 



' Monograph, vol. ii, 1906, p. 5. 



* Jenaische Zeit. f. Naturwiss., vol. Ii, 1914, p. 225, fig. 4 : a fine monograph 

 on the anatomy of the central German speciea with a copious bibhography. 



