CHLOROSTOMA, 175 



to 6, the upper ones with a strong carina midway between the 

 sutures, the last carinated at the i^eriphery and above, generally 

 showing a less prominent carina on the base near the periphery ; 

 aperture oblique, columella oblique, arcuate ; umbilicus broad and 

 deep, with a spiral rib within. 



Alt. 26, diam. 40 ; alt. 35, diam. 44 mill. 



W. coast of S. America, from Callao io Valparaiso. 



Trochas lactuosus D'Orb., Voy. dana V Amer. Merid., p. 409, t. 

 76, f. 16-19.— Philippi, Conchyl. Gab., p. 153, t. 25, f. 4, 5.— 

 Fischer, Coq. Viv., p. 106, t. 31, f. 3. — T. bicarinatus Pot. et 

 Mich., Galerie, i, t. 30. f. 1-3 (not T. bicarlnatas Lam., a fossil 

 species). — T. carimdiis Koch, in Philippi, Abbihl., Trochus, t. 2, f. 

 3 (not T. carinatns Borson, a fossil species). — CJdorostoma tropido- 

 phorum A. Ad., P. Z. S., 1851, p. 183. 



The wide umbilicus and strongly keeled whorls separate this 

 form from the other species. 



C. TRiDENTATUM Potiez et Micliaud. PI. 28, figs. 47, 48. 



Shell minutely peyforaie, conoidal, elevated, heavy and solid, 

 black or jiurplish ; wdiorls 5 to 6, slightly convex, smooth, the last 

 with rounded periphery ; base somewhat flattened, deeply eroded in 

 front of the aperture; aperture small, obIi(|ue, the outer lip thick 

 and Urate wdthin, the columella short, oblique, distinctly tridentate 

 at the base ; umbilicus circular, minute. 



Alt. 19-22. diam. 15-18 mill. 



Coasts of Peru and Chili. 



Monodonta tridentata P. ET ISI., Galerie. du Mus. de Douai, i, p. 

 321, t. 29, f 16, 17. — Trochus tridentatus Phil., Conchyl. Cab., p. 

 153, t. 25, f. 3.— Fischer, Coq. Viv., p. 172, t. 57, f 2.—T. tridens 

 Mkk. in Philippi. Abbild., Trochus, t. 4, £ 10. — T. stenomphalus 

 Jonas, Zeitschr. f. Mai., , p. 114. — T. microstomus D'Orbigny, 

 Voy. dans CAmcr. Merid., p. 410, t. 76, f. 20, 21. 



* * * 

 ( Omphalius.) 

 C. viRiDULUM Gmelin. PI. 29, figs. 54-56. 



Shell umbilicate, conoidal, solid, whitish-grayish or greenish, 

 radiately striped above with crimson or rich brown, beneath spotted 

 or radiately striped with the same color; spire rather obtuse, short; 

 whorls 6, convex, encircled by spiral lirre which are n.ore or less 



