282 DESCRIPTION OF A COLLECTION OF FOSSILS, 



seen in such monographs as d'Orbigny's Pal. Francaise. The operculum figured 

 in that work (Terr. Cret., vol. ii. PI. 186 bis, figs. 15-17) evidently belongs to this 

 genus. The author declares himself unable to associate it with its proper shell, 

 and says of the two operculi figured that they are " au moins un confirmation de 

 leur bon classement dans le genre Turbo. L'un d'eux est tres-remarquable par ses 

 tours tres-rapproches, comme chez les Trochus proprement dits." 



In virtue of the general form and the multispiral operculum, I believe this 

 genus to belong near to Gibbula, despite the fact of the calcareous nature of the 

 operculum. All of the genera in the Tarbinidce approaching it in form have that 

 member markedly paucispiral, and constructed in an entirely different manner. 



P. Peruanus, n. s., PI. 40, fig. 8. 



Shell small, robust, spire moderately elevated, sides regularly sloping ; whorls 

 six, flattened on their upper sides; body whorl flattened and sloping above, rounded 

 and bi- or tri-carinate on the margin, and slightly convex below. Surface marked 

 by about six heavily beaded ribs above, the uppermost of which makes the sutural 

 margin; the two on the sides are the largest, and when a third exists it is slightly 

 smaller and placed below the other two; under surface covered with six or seven 

 similar ribs, the last forming a crenulated margin to the umbilicus, which is minute 

 and apparently imperforate. Aperture sloping subquadrate ; outer lip simple ; 

 inner lip bordered by a flattened pillar lip, the anterior part slightly overlapping 

 the umbilicus. 



Locality. From the coal mine of Pariatambo and from the Cerro del Ventanillo, 

 Liassic. 



HELCION, Montf. 



H. CARBONARius, n. s., PI. 40, fig. T, Ta. 



Shell small, nearly circular, thin ; apex subcentral, about a third as high as the 

 diameter of the shell ; surface polished and marked by prominent lines of growth. 



Locality. With the preceding. 



LAMELLIBRANCHIATA. 



PANOPiEA, Menard. 



P. UNDULATA, n. s., PI. 40, fig. 9. 



Shell sub-elliptic, moderately convex ; base nearly straight in the middle ; 

 beak prominent; anterior end unknown; posterior gaping, nearly semicircular and 

 with the upper and middle margins reflexed. Surface covered with regular, 

 rounded concentric ribs and subacute interspaces ; the ribs larger on the middle 



