MADE BY DR. ANTONIO RAIMONDI IN PERU. 291 



anterior end, not approximating; anterior end nearly vertical, most prominent 

 near the base; posterior face abruptly truncated; base nearly straight, slightly 

 emarginate and a little the most prominent directly under the beaks ; area small, 

 short; internal plate moderate; internal margin entire. Surface unknown; the 

 cast shows traces of numerous rather small radiating ribs. 



Figures. Natural size. 



Locality. Neighborhood of Ollon. Considered by Dr. Raimondi "Jurassic"?", 

 but more probably Cretaceous, both from this and the associated fossils. 



Remarks. A large, not very perfect cast, the upper part of the posterior end 

 being broken away, so as to destroy the shape of the point of junction between 

 the area and the posterior margin. Associated with it is a cast of a smaller shell 

 (figs. 8, 8a), an inch across, apparently of the same species, but with a more convex 

 base and flatter sides; the latter difference, however, being one that might be 

 anticipated, from the difference of age. The species cannot be confounded with 

 Cue. dilatata, d'Orb., from the Cretaceous of Bogota, its nearest South American 

 ally, having much higher and more approximating beaks, a straighter base, and 

 less produced posterior end. In Cucullcea dilatata the beaks are very wide apart 

 and the lower posterior end much more produced. 



T. BKEVis, D'Orb. (sp.), Amer. Merid., p. 89, PI. 20, f. 2-4. 



There is a small shell, one inch in diameter, from the " high table land two 

 leagues from Cajamarca, at a height of more than 3500 metres," which resembles 

 d'Orbigny's figure so closely that I believe it to be the young of that species. 

 D'Orbigny and Raimondi both consider it Cretaceous, and the fossils associated 

 with it seem to confirm the opinion. 



T. Peruana, n. s., PI. 41, fig. 9, 9a. 



Shell trapezoidal, very oblique ; beaks anterior, approximated, and incurved ; 

 area a little longer than half the length of the shell ; posterior end very sloping ; 

 base nearly straight. Surface unknown. 



Figures. Natural size. 



Locality. Neighborhood of Ollon ; considered Cretaceous by Dr. E-aimondi. 



Remarks. A single cast, retaining none of the surface, but showing by its form 

 and by the posterior plates, the generic characters sufficient to place it with cer- 

 tainty, and by its outlines enough specific characters to enable it to be identified. 

 No similar species has been described from the South American secondary rocks. 



?Arca ovalis, n. s., PI. 41, fig. 10, 10a. 



Shell moderate in size, convex, oblique, very much elongated from beak to base; 



