TROCHUS. 63 



the upper surface about 7 spiral beaded lira?, the interstices oblique- 

 ly finely striate ; base subplanulate, concentrically sculptured with 

 about 7 or 8 beaded lira? ; aperture rounded rhomboidal, the outer 

 and basal lips thick, evenly and finely plicate within ; columella 

 oblique, deeply entering, conspicuously folded near its insertion, its 

 edge denticulate near the base, and passing into the basal margin 

 with a regular curve ; parietal wall bearing a white wrinkled callus, . 

 the untbilical margin of which is dentate; umbilicus wide, deep, 

 scarcely narrowed as it penetrates, bordered by a strong acutely 

 dentate rib. Alt. 13-16, diam. 18-20 mill. 



Guinea; Gaboon; Liberia. 



Trochus guineensis GMEL. Syst. Xat. xiii, p. 3574, no. 49, 1788. 

 PHILIPPI, Conchyl Cab. p. 79, t. 14, f. 9. FISCHER, Coq. Viv. p. 

 221, t. 72, f. 3. 



This species, together with T. villanus constitutes a group which 

 differs from the typical forms of Clanculus in lacking the strong 

 tooth at the base of the columella. 



T. VILLAXUS Philippi. PI. 11, figs. 58, 59 ; pi. 14, fig. 28. 



Shell conical, very solid, cinereous-olive or purplisji, lighter 

 beneath, sparcely dotted with black; whorls about 6, slightly con- 

 vex, spirally lirate, the last encircled by about 14 granose separated 

 lira?, of which about 6 are on the upper surface, their interstices 

 bearing spiral stria? ; last whorl obtusely angular at the periphery, 

 slightly convex beneath, a little descending anteriorly ; aperture 

 rounded-tetragonal, outer and basal lips plicate within, columella as 

 in T. guineensis but longer; umbilicus narrow, deep, parietal wall 

 slightly calloused, wrinkled. Alt. 22, diam. 22 mill. 



W. African coasts ; Guinea; Gold coast; Gaboon. 



Mondonta villana PHILIPPI, Zeitschr. f. Mai. 1846, p. 101. 

 Trochus villanus PHIL. Conchyl. Cab. p. 74, t. 14, f. 3. FISCHER, 

 Cog. Viv. p. 220, t. 72, f. 2. 



More elevated than T. guineensis, less carinated at the periphery, 

 and with narrower umbilicus. The parietal callus is much heavier 

 in T. guineensis. 



