TROCHUS. 63 



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

 ly finely striate; base subplanulate, concentrically sculptured with 

 about 7 or 8 beaded Vivx ; aperture rounded rhoniboidal, the outer 

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

 oblique, deeply entering, conspicuously fielded 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 umbilical 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 gidneensis Gmel. Syst. Xat. xiii, p. 3574, no. 49, 1788. — 

 Philippi, Conchy L Cab. p. 71), t. 14, f 9. — Fischer, Coq. Viv. p. 

 221, t. 72, f. 3. 



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

 diflfers from the typical forms of Clanculus in lacking the strong 

 tooth at the base of the columella. 



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



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

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

 vex, sj)irally lirate, the last encircled by about 14 granose separated 

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

 bearing spiral stripe ; 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 coads ; Guinea; Gold coast; Gaboon. 



Mondonta villana Philippi, Zeifschr. f. Mai. 1846, p. 101. — 

 Trochus villanus Phil. Conchyl. Cab. p. 74, t. 14, f. 3. — Fischer, 

 Coq. Viv. p. 220, t. 72, i\ 2. 



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

 and witli narrower umbilicus. The parietal callus is much heavier 

 in T. guineen.-is. 



