CHLORQSTOMA. 165 



a. Strongly plicate ; base spirally lirate, C. carpenteri. 



b. Base smooth. 



a. Obsoletely plicate, C. pfeifferi. 



b. Entirely smooth, C. achates. 



C. ARGYROSTOMA. Gmelin. PL 25, figs. 11, 12. 



Shell imperforate, conical, solid, heavy, black, except the eroded 

 first whorls which are yellow, the base lighter, olive or pinkish ; de- 

 pressed ; whorls about 7, finely longitudinally corrugated, and 

 much less obviously spirally sculptured, the longitudinal sculpture 

 obsolete on the base ; aperture very oblique, smooth and nacreous 

 within ; outer lip edged with black ; columella oblique, decidedly 

 dentate midway, and frequently less markedly so at the base ; um- 

 bilical tract covered by a heavy green callus. 



Alt. 40, diam. 45 mill. 



Philippines ; Chinese and Japanese Seas. 



Trochus aryyrostomus GMEL., Syst. Nat., xiii, p. 3583. LISCHKE, 

 Jap. Meeres-ConchyL, p. 96, t. 7/f. 3-5. FISCHER, Coq. Viv., p. 105, 

 t. 29, f. 4 (Turbo). T. distinguendus DUNKER, Molluska Japonica, 

 p. 22, t. 3, f. 1. (1861.) 



An abundant and variable species. It may be separated from 

 the following forms by the imperf(*rate base, green or olive umbili- 

 cal callus, and finely, regularly plicate upper surface. 



Var. DISTINGUENDA Bunker. PL 26, fig. 20. 



Longitudinal folds less strong, close ; base smooth ; umbilical 

 callus white. Alt. 18, diam. 20 mill. 



Japan. 



C. NIGERRIMA Gmelin. PL 25, figs. 9, 10. 



Shell umbilicated, rather depressed conical, solid, black or pur- 

 plish-black, lighter beneath ; spire conic, sutures impressed ; whorls 

 about 6, very obliquely striate, longitudinally finely corrugated, the 

 folds small, dichotomose a short distance beneath the periphery, very 

 regular and close ; base nearly flat, smooth ; periphery bluntly 

 angular ; aperture very oblique ; columella toothed in the middle 

 and more obsoletely at the base, expanding above in a callus half 

 surrounding the umbilicus and partly covering it. 



Alt. 20, diam. 25 mill. 



Japan. 



