Mr. T. D. A. Cockerell's Notes on Slugs. 97 



IX. — Notes on Slugs, chiefly in the Collection at the British 

 Museum. By T. D. A. COCKERELL. 



[Continued from vol. vi. p. 390.] 



V. Hblicasioninje. 



The Limacidae include a number of groups whicli may well 

 be regarded as subfamilies, diifering in the shell, the presence 

 or absence of a caudal mucus-pore, and in various other 

 ways. The subfamily Helicarioninfe may be made to include 

 all those forms which have a mucus-pore, but do not possess 

 a typically Zonitoid or Helicoid shell ; but this definition is 

 rather a matter of convenience than an expression of naturally 

 defined limits, for it is actually impossible to draw any hard- 

 and-fast line between certain Ilgah'na-Yike forms and their 

 Vitrinoid allies. Similarly, were it desirable to divide the 

 group into Vifrina-\ike and slug-like forms, the genera 

 Girasia and Austenia would offer so many puzzling interme- 

 diates that no satisfactory limits could be found. It thus 

 happens that, although my pui-pose is to treat of slugs^ I am 

 obliged to include a variety of genera which possess spiral 

 shells. 



It is necessary, however, to exclude from the Helicarioninse 

 certain forms which are superficially very similar to them. 



Otoconcha, Hutton, resembles a Helicarion, but has a ribbed 

 jaw and no caudal mucus-pore. 



Hemphilliay Bid. & W. G. Binn., from Oregon, is very 

 much like a Girasia in appearance and has a mucus-pore; 

 but its jaw is ribbed. Binnega, J. G. Cooper, resembling a 

 Helicarion, has, like Otoconcha, a ribbed jaw and no mucus- 

 pore. The true Vitrinina?, consisting of Vitrina and allied 

 genera, lack a mucus- pore, but otherwise stand closest to 

 Helicarioninge, 



The teeth of Helicarioninae are of the normal Limacid type, 

 that is to say the centrals have a large central and two smaller 

 lateral cusps, and the laterals are bicuspid, although on both 

 centrals and laterals there may be obscure additional cusps. 

 The centrals and laterals are of the quadrate type, the mar- 

 ginals aculeate. 



Durgella, W. T. Blanford, is a Vitr{naA\kQ, genus from the 

 Indian region, with six species, according to Godwin- Austen. 

 It has a mucus-pore, but the dentition is very different from 

 Helicarionina;, and is suggestive of Selenitidge. It may 

 perhaps form a subfamily — Durgellinse — under Selenitidte. 



Ann. & Mag. N. Hist. Ser. 6. Vol. vii. 7 



