114 JOURNAL OF CONCHOLOGY, VOL. I4, NO. 4, OCTOBER, I913. 



"This species of Cyprma requires to be studied anew, because 

 Crosse considers it distinct ; Sowerby judges it a variety of C. nebii- 

 losa ; and Roberts looks upon it as no more than a modification of 

 C. pyrnm. I have seen in Paris, in the collection of my friend 

 Dautzenberg, examples classified as C. petitiana (half-grown) which 

 appear to me only a variation of C. pyrmn, and two others in the 

 Jousseaume collection nearer to Sowerby's figures 354 and 355 in 

 Thesai/rus Couchyliorinri and somewhat distinct from those of Daut- 

 zenberg. Not having these at my disposal at the time of writing, I 

 cannot decide which of the three authors is most in the right. Of all 

 methods, comparative examination of the characters of the aperture, 

 size, position, and number of the teeth, will serve more than the 

 colouration of the shell to establish or not the resemblance with 

 C. pyrum and nebiilosa, because I will call attention here to the fact 

 that the var. nyinphx of C. onyx Linne, so different from the type in 

 its colour, is identical in form and teeth of the aperture." 



I quite recently sent my specimen to Mr. J. Cosmo Melvill for his 

 opinion ; he writes to me : — 



"Your shell is indeed a fine C. petitiana; it exactly agrees with 

 mine, a fine live specimen, but only half the size of yours j it has 

 been considered a variety of C. pyruvic but I don't now think it is ; 

 it seems to possess distinctive qualifications." 



I have seen another example in the collection of Mr. Loftus Byne, 

 but this also is quite small, clearly showing two narrow white zones, 

 precisely the same as in the figure of Sowerby, before mentioned ; 

 this I take to be not full grown. 



The dimensions of my shell are : — 



Length, 31 mm. • breadth, 19 mm. ; altitude, 15^^ mm. 

 Habitat, River Gambia, West Africa. 



C. nebulosa Kiener. — 



I cannot at all agree with Roberts in making this a variety of 

 C. zonata Chemn., its shape, markings, and general appearance being 

 so widely distinct. In shape it is much more ovate, less pyriform, 

 the anterior extremity not nearly so attenuated and produced, with 

 the terminal blotches much less evident ; in C. nebuiosa also the 

 right lateral border is crassated and wider, obtusely angulated, the 

 marginal spots ash-coloured and fainter. The dorsal surface is also 

 ash-coloured, with clouded ferruginous markings, and no zonal 

 bands; its base is rosy-white or straw-coloured. In contrast to this, 

 C. zonata is more pyriform, rounded at the sides, extremities pro- 

 duced, thickish, laterally margined at the extremities, the anterior 

 end subattenuate and truncate ; ground colour of the back pale 



