/ DESCRIPTIONS OF CARIBBEAN MIOCENE FOSSILS. 347 



P. Paranensis, d'Orb., PL 45, fig. 24. 



Mr. Conrad and I studied this species and Conrad's P. Madisonius in detail, 

 and we were both satisfied of their identity, the slight variations being geographi- 

 cal only. My fossil, like the South American, has a few more ribs, but the num- 

 ber varies in Madisonius ; the details of sculpture are the same. My specimen is 

 a little oblique, probably from pressure. 



JANIRA, Schum. 

 J. SORER, Gabb, St. Domingo Memoir, Tr. Amer. Pliilos. Soc, vol. 15. 



A poorly preserved specimen in the Newberry lot from Gatun. 



PLURONECTIA, Swains. 

 P. Lyonii, Gabb, n. s., PI. 45, fig. 25a-b. 



Shell large, thin, flat, perfectly plain on the surface, marked by faint lines of 

 growth, or in young shells, showing faint radiating undulations corresponding 

 with the internal ribs. Hinge line perfectly straight and with the* teeth inclined 

 slightly downwards from the beak. Inner surface costate by small solitary ribs 

 not running in pairs. These may or may not show signs of their existence 

 through to the outer surface. 



Figure. Natural size. 



Locality/. I found it not rare, but very difficult to obtain on the shore of the 

 Eeventazon river, in front of Sapote, but at a lower stratigraphical level. The 

 rock is very tough, and it could only be obtained by chipping off in minute pieces. 

 The specimen figured consists of seventeen fragments. Also found in the New- 

 berry lot from Gatun. 



From P. pleuronectes and P. Japonica, it difi'ers in being slightly more convex 

 near the beaks, the internal ribs show less tendency to run into pairs, and the ears 

 are proportionately much larger. The specimen figured, a lower valve, has the 

 cardinal margin of the ears, a straight line across from angle to angle, and the 

 teeth inclined slightly downward from the beak. In the two above-named species 

 the cardinal margins are elevated from the beak to the angles, and the teeth are in 

 a right angle. P. Mortoni of the North American Miocene is a much larger shell, 

 and the ears are proportionately still smaller, and are truncated on the outer angles. 

 P. Clintonius has radiating striae, sometimes nearly obsolete, but always visible, 

 and sometimes developed into even low ribs. P. jpapyracea, Gabb, from Sto. Do- 

 mingo, only two inches in diameter, is markedly inequivalve ; the ears are very 

 small, and the upper lines very oblique. P. Darwinii, Sby. (Pecten), South America, 

 is higher shouldered, and the ears are much smaller than this. 



