288 DESCRIPTION OF A COLLECTION OF FOSSILS, 



of Coniaca, Dept. of Huancavelica. The latter at the height of 8200 metres. 

 D'Orbigny's specimen came from las Palmas, Prov. of Socorro, U. States of Colom- 

 bia, and was only an internal cast. 



Remarks. Dr. Kaimondi refers the first to the Cretaceous, and the second to 

 the Jurassic. Generically this shell belongs to that group, or subgenus, separated 

 by Blainville under the subgeneric title of Cardiocardites (not id. Meek), and to 

 which Dr. Gray subsequently gave the name of Agaria. The Carditas have been 

 so divided up into genera and subgenera that, as in this case, the distinction rests 

 almost, if not entirely, on the outline of the shell, and, while the typical form is 

 marked enough, a regularly gradated series of species, recent or fossil, can be pro- 

 duced to show that this is absolutely of no value. 

 Cardita (Ctclocardia) circularis, n. s., PI. 41, fig. 3, 3a. 



Shell nearly circular, compressed ; beaks somewhat anterior, not very promi- 

 nent ; anterior and posterior ends and base forming continuously three-fourths of 

 a nearly perfect circle; cardinal margin sloping convexly; directly under the beaks 

 the anterior end is slightly excavated; lunule very small; surface covered by 

 twenty-seven or twenty-eight regular radiating ribs, each producing a corresponding 

 crenulation on the inner margin. 



Figures. Natural size. 



Locality. " Snow mountains to the left of the road between Chonta and Que- 

 vopalco ; Province of Huamalies ; at a height of more than 5000 metres." Re- 

 ferred doubtfully to the Cretaceous. 



Remarks. Its remarkably circular form will serve to distinguish this shell from 

 all of its congeners. The specimen has a polished appearance, as if it had been 

 long carried in the pocket, and the fine details of the surface are completely worn 



off. 



TRIGONIA, Brug. 



T. Bronnii, Agas., Mem. sur les Trigonies, p. 18, PI. 5, fig. 19. 

 Lyrodon clo.vellatum, Bronn, Lethsea, PI. 20, f. 3. 



id., Goldf., Petr. Germ., p. 200, PI. 136, f. 6 o.&. 

 Not T. clavellata, Sby., Min. Conch., PI. 81. 



A beautiful specimen, agreeing in every detail of outline and ornament with 

 Agassiz's figure and description. Agassiz says the species is peculiar to the Upper 

 Jurassic. Our specimen is from the "immediate vicinity of Jauja; height of 3500 

 metres." 

 T. LoRENTi, Dana, Wilkes' Exped. Rep., p. 721, PI. 15, f. 2. 



From the Island of San Lorenzo, near Callao. From its type, evidently Juras- 



