MADE BY DR. ANTONIO RAIMONDI IN PERU. 285 



face covered by radiating ribs, which become faint at each end. A slight narrow 

 depression runs parallel with the posterior cardinal margin, bordered by a rounded 

 angle. 



Figure. Natural size. 



Locality. Between Combayoa and Polloc; Dept. of Cajamarca. From a lime- 

 stone which. Dr. Eaimondi says, "appears to be Jurassic." Two other specimens, 

 referred doubtfully to the same species, are from the hacienda of Macanga, which 

 locality is almost certainly Cretaceous. 



P. ZiETENii, A gas., Etud. sur les Myes, p. 54, PI. 3, f. 13-15. 



P. fidicula., Zieten (not Sby.). 



P. Zieteni., Baj'le & Coquand, Mem. G. Soc. Fr., 2 s., v. 4, p. 26, PI. 7, f. 8. 



Our shell is the same as that figured by the last authors, though I think it is 

 doubtful if this is the same as the European species ; it differs in the posterior 

 end and is much more strongly ribbed than Agassiz's figure. It is from the Juras- 

 sicC?) rocks in the neighborhood of Ollon. 

 P., sp. indet. 



From the Liassic coal mines of Pariatambo there is a single small Pholodomya, 

 too much distorted for a very satisfactory determination, and entirely unfitted for 

 description if new, since the outline is destroyed. In style it resembles P. echinata, 

 Agas., but has fewer radiating ribs. 



HOMOMYA, Agas. 

 H. INCURVA, n. s., PI. 40, fig. 13, 13a. 



Shell convex, inequilateral; beaks prominent, placed about a third of the 

 length from the anterior end, and strongly incurved ; anterior end most prominent 

 just above the middle, above which |)oint to the umbones it is slightly concave, 

 and below which it unites by a broad curve with the broadly and regularly rounded 

 bases ; posterior cardinal margin sinuous ; posterior end obliquely rounded, sub- 

 truncate above, narrowly rounded at its most prominent part in the middle. Sur- 

 face marked by numerous small rounded concentric ribs. 



Figures. Natural size. 



Locality. From the neighborhood of Ollon. Cretaceous or Jurassic 1 



RemarA's. Easily distinguished by its short, compact form and its strongly 

 incurved beak. The concentric lines vary in strength in different specimens 5 in 

 some they are a tenth of an inch across, while in others they diminish to mere 

 lines of growth. I cannot think this indicates two species, because, as is usual in 

 such cases, the undulations are strong on the beaks, and the fine lined forms show 



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