Zoological Society : — Dr. J. E. Gray on Urocyclus. 331 



ZOOLOGICAL SOCIETY. 



May 24, 1864.— Prof. Huxley, F.R.S., V.P., in the Chair. 

 On Urocyclus, a New Genus of Terrestrial Gastero- 



PODOUS MOLLUSCA FROM AFRICA. By Dr. J. E. GRAY, 



F.R.S., ETC. 



Dr. John Kirk has kindly sent to the British Museum, with some 

 other Mollusca in spirits, a specimen of a Slug from the Zambesi. 



Naked Terrestrial Mollusca seem rare in that country, for Dr. 

 Kirk says it is the only species of Slug that he observed during 

 his journey : he thinks that the country is probably too dry for 

 them. It was found on some floating weed near the mouth of the 

 river Zambesi. It was not uncommon. This Slug forms a new 

 genus, which may be thus named and described : — 



Urocyclus. 



Body elongate, attached its whole length to the upper surface of 

 the foot. Mantle shield-like, uniformly granular ; a small and round 

 deep pit in the middle of the hinder margin. Shell ? Sub- 

 caudal gland very large, deep, circular, surrounded by a broad trans- 

 versely grooved edge. The respiratory aperture on the middle of 

 the right side of the mantle ; orifice of generation at the base of the 

 right tentacles. Tentacles four, retractile ; lower small. 



This genus is exactly like a Limax or an Avion in external form ; 

 but is immediately to be distinguished from either of them by the 

 large size of the deep glandular pit, which is situated on the upper 

 surface of the tip of the tail, and is surrounded by a broad, smooth, 

 raised edge, marked with numerous transverse grooves. 



The genus Milax is said to have two small pores near the hinder 

 edge of the mantle, which may be analogous to the single pores in 

 the mantle of this genus. The genus Milax is certainly destitute of 

 any subcaudal gland or pore, and is referred to the family Limacidse ; 

 while the genus here described is peculiar for the large size and 

 general development of the subcaudal pore. 



In the pores on the hinder edge of the mantle it may be allied to 

 the Limax noctilucus of D'Orbigny and the Phosphorax noctilucus 

 of Webb and Berthelot, of Teneriffe ; but this animal is so very im- 

 perfectly described and badly figured that it is not easy to under- 

 stand it. Ferussac, in the 'Bulletin d. Sci. Nat.' 1 821, x. 300, in which 

 it is first noticed under the name of Limax noctilucus, only observes, 

 " it is furnished with an aperture in the mantle similar to that in 

 Avion extvaneus, from which escapes a phosphorescent matter." 

 Now Avion extvaneus is evidently a Dvusia ; and the hole in the 

 mantle is the space left between the reflexed edges of that organ, 

 exhibiting part of the shell. The figure given by D'Orbigny, in Fe- 

 russac's ' Mollusca,' p./6,t.2. f. 8, exhibits the body contracted, and 

 the hinder part produced into a marginal disk, which is said to be lucid 

 green and phosphorescent in the dark. The tail is described as 

 rounded, and no mention is made of any subcaudal gland of any kind ; 

 so that it can scarcely be the genus here described ; for the large, 



