250 DR. J. E. GRAY ON THE GENUS UROCYCLUS. [May 24, 
marginatis : rostro nigro, apice utriusque mandibule distincte 
pallide cornea ; pedibus corneis. 
Long. tota 19°5, alee 6°5, caudee 10°8, tarsi 3°8. 
Hab. In Guiana et Amazonia sup. 
Obs. Sp. a prec. alis rufis, torque lato, et rostro bicolore primo 
visu distinguenda ! 
4. On Urocycuus, 4 New Genus or TERRESTRIAL GASTERO- 
popous Mo.uuusca FROM AFRICA. By Dr. J. E. Gray, 
F.R.S., erc. 
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 :— 
URocycuvs. 
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 Limaz or an Arion 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 Mila 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 Milaz is certainly destitute of 
any subcaudal gland or pore, and is referred to the family Limacide ; 
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- 
standit. Férussac, in the ‘Bulletin d. Sci. Nat.’ 1821, x. 300, in which 
it is first noticed under the name of Limaw noctilucus, only observes, 
‘it is furnished with a similar aperture in the mantle as that in 
Arion extraneus, from which escapes a phosphorescent matter.” 
Now Arion extraneus is evidently a Drusia; and the hole in the 
mantle is the space left between the reflexed edges of that organ, 
