MADE BY DR. ANTONIO RAIMONDI IN PERU. 293 



with it ; but they can be at once distinguished by the more terminal position of 

 the beaks of this, and its cuneiform shape— while in that, the beaks are nearly 

 central, and the posterior cardinal margin, instead of sloping down a trifle con- 

 vexly, giving a general wedge shape to the shell in this, is in that markedly 

 concave. 



N., sp. indet. 



A large heavy convex species, with very prominent hinge teeth and subcentral 

 beaks, represented by a single cast from near OUon, 



LIMA, Brug. 



From the " limestone of Socabon of the mines of the hill of San Antonio of 

 Morococho, on the road from Lima to Jauja, at a height of 4200 metres," there is 

 a fragment, the impression of perhaps half of the surface of a Lima or Plagiostoma 

 of the type characteristic of the European Lias. It was, when entire, a little more 

 than two inches long, and marked by numerous fine, equal, radiating ribs. 



Also, from the Liassic limestone of the Cerro de la Ventanilla is another Lima 

 an inch long. The shell is preserved, but it is attached by its outer surface and 

 only shows the interior of the valve, and without the ears. The surface, as seen 

 through the shell, is marked by rather large radiating ribs, strongest on the poste- 

 rior half of the shell. . 



PECTEN, Linn. 

 P. Raimondii, n. s., PL 42, fig. 1, la. 



Shell oblong, flattened, equilateral, slightly inequivalve, closed; surface of both 

 valves covered with strong radiating ribs, about 15 or 16 on each valve. These 

 ribs are surmounted by three ridges, and the intervening, grooves carry also one or 

 three small radiating lines; all crossed by strong lines of growth becoming slightly 

 squamose on crossing the ridges ; anterior right auricle emarginate. 



Figure 1, natural size; la, a magnified cross section of the ribs. 



Locality. From the " hill of Potosi, on the road from Lima to Jauja, in the 

 mineral region of Morococho." 



Remarks. The inequal convexity of the two valves places this shell in the sub- 

 genus Chlamys, Bolt., according to H. and A. Adams. It is of the type of P. 

 Faujasii and P. cretosus, which it resembles in the style of the ribs, while it differs 

 in their details and in general form, being a shorter and rounder shell. 



P. ARGENTARITJS, n. s., PL 41, fig. 12, 12a. 



Shell flattened, base rounded ; sides and ears unknowif ; surface marked by 

 65 



