LAMELLIBEAKOHIATA OF THE LOWEE MAELS. 189 



Pholas ? lata, n. sp. 

 Plate XXV, Fig. 17. 



Shell large and proportionally very broad between the dorsal and 

 basal margins, the relative heiglit and length being about as two to three, 

 respectively. The general outline is slightly ovate, widest at the anterior 

 end and gradually narrowing posteriorly, the beak being a little in advance 

 of the middle and showing somewhat above the cardinal line in the shghtly 

 compressed and somewhat crushed specimen of an internal cast of a left 

 valve, the only one yet seen. Anterior and posterior ends rounded, the 

 latter one most narrowly so; basal hne shghtly emarginate just behind the 

 middle of its length ; cardinal line apparently arcuate throughout. Surface 

 of the shell, as shown on the cast, convex, with a broad sulcus passing 

 across the valve from beak to base, reaching the latter behind the middle. 

 Anterior to the sulcus the surface is radiately ribbed, the rays being some- 

 what alternate in size over a portion of the space. At the bottom of the 

 broad sulcus there is a single larger and stronger rib, which passes from 

 the beak directly to the base of the shell, which it reaches at the point of 

 greatest emargination. Posterior to this larger rib the surface is destitute 

 of radiating lines, the surface being marked only with broad, irregular, 

 concentric sulci, which extend over the entire surface parallel to the margin 



of the shell. 



This is a pecuharly formed shell, and does not appear to belong strictly 

 to the genus Pholas, The only figure of a similar species which I have 

 been able to find in any work to which I liave access is that given on Plate 

 603, Sow., Mineral Conch., under the name PJwIas? compressa, and so given 

 and retained in all the hsts and catalogues to which I have access. The 

 species is from the Kimmeridge clays of Shotover Hill, England, and is not 

 quite half as large as the New Jersey specimen, while it is much broader 

 proportionally and also more strongly ribbed on the posterior part. The 

 shell undoubtedly belongs to the PJwIadidce, but certainly cannot be a true 

 PJiolas ; but as there are none of the hinge features present on the specimen, 

 or even the entire external form, I do not think it prudent to suggest a 

 generic name. 



