Mr. T. D. A. CockerelPs Notes on Slugs. 101 



they at present appear. It may be even that the whole of 

 the present group will have to form a series of subgenera only 

 under Urocyclus, in which case T. Heynemanni, Simr., would 

 require a new name. The question, what constitutes a generic 

 unit, is an extremely difficult one to answer ; and in the face 

 of the fact that genera are not by any means so naturally 

 defined even as species one is driven to treat the whole 

 matter as essentially one of convenience only. 



For my own part I should prefer not to multiply genera 

 more than appears absolutely necessary, and to call the minor 

 groups simply subgenera, groups, or sections. This, how- 

 ever, is no better than an individual opinion, not at all shared 

 by a numerous body of naturalists whose judgment commands 

 respect. 



Buettneria is said to have a dart-gland united with the 

 penis, and the structure is figured by Simroth. It is worth 

 noting that Cryptosoma prcestans, according to Godwin- 

 Austen's figure, has a precisely similar structure, called by 

 Godwin-Austen a " cuecum or kale-sac." 



Urocyclus Kirkii, Gray. 



There is, in the British Museum, a specimen marked (in 

 Dr. Gray's handwriting, as Mr. Atkinson informs me) 

 "Urocyclus KirJcii, Cent. Africa, Dr. Kirk, 11 May, 1864." 

 This is evidently Gray's type, although it is not very much 

 like his figure in Proc. Zool. Soc. 1864. It agrees with the 

 figure of it given by Heynemann, Jahrb. 1884, Taf. i. fig. I. 



From it I made the following notes : — 



Mantle finely reticulate, 17| millim. long, with a round 

 posterior opening about 2 millim. diam., whence run two slight 

 grooves as figured by Heynemann. Respiratory orifice 10£ 

 millim. from anterior border of mantle. Mucus-pore as figured 

 by Heynemann. Colour ochreous, bands blackish, and body 

 with a sort of blackish interstitial marbling. Mantle greyer. 

 Neck dark above. Sole unicolorous, central zone slightly 

 narrower than either lateral. 



Urocyclus pallescens, sp. n. 



Length (in alcohol) 3.1^ millim.; uniform pale greyish 

 ochre, spotless. Mantle reticulated, the opening only a narrow 

 slit or small, rather oblong hole, very much smaller than in 

 Kirkii, and inconspicuous. Mucus-pore smaller than in 

 KirJcii. Respiratory orifice as in Heynem ami's figure of 

 jasciatus. Reticulation on body in longitudinal squarish 



