MIOCENE MOLLUSCA AND CRUSTACEA. ' 31 



the ribs and on their sides. This feature becomes very conspicuous on the 

 larg-er specimens. Besides this, the hjwer valve is much more depressed 

 or flattened than tlie upper. The number of ribs on the more convex valve 

 is sometimes seventeen or even eighteen, showing considerable variation. 

 I have not seen any very large individuals from the New Jersey localities, 

 and few of more than Ij inches in diameter. Some of the casts from the 

 brown clays, however, indicate shells nuicli lai-ger than this, and some 

 fragments of valves froni near Shiloh, in the collection at Rutgers College, 

 indicate shells of fully 4 inches in width, but no specimens showing more 

 than one-sixth part of the entire valve have been collected. 



The species bears some resemblance to Pecten Jeffersonins Say, but is 

 very readilv distinguished by the more numerous and smaller ribs and by 

 their squamose, almost ,spino.se stria=. 



Foniiatioii tuuJ UxaJitifS : The New Jersey examples, all quite frag- 

 mentary except the very young individuals, are from the gray Miocene 

 marls near Shiloh and Jericho, and as casts from the brown marly clays 

 near the same places in New Jersey. The species is (juite connnon and of 

 larger size in the Miocene at Yorktown, Petersburg and vicinity, in Vir- 

 ginia; it also occurs in South Carolina. 



Pkcten A-ICENAinUS? 

 Not Jigiired. 



Pecten vicenurius Conrad: Proc. Acad. Nat. Sci. Phil., vol. 1, 1st series, p. 306; op. 



cit. 1862, p. .382; Meek, Cbeck List Mioc. Foss., p. 4. 

 Pecten vicenaritosiJoii: Heilprin, Proc. Acad. Nat. Sci. Phil., 1887, pp. 400 aud -102. 



" Suborbicular, inccpiivalve, the upper valve veiitricosi', the inferior 

 plano-convex; ribs about twenty, somewhat flattened on the back; ribs of 

 the superior valve narrow and more distant than those of the inferior valve; 

 surface of Ijoth with crowded, regular concentric wrinkles; ears e([ual, uKtd- 

 erate in size, sinus of inferior valve not profound." (Conrad.) 



A number of small fragments of a pectenoid shell of small size, which 

 were obtained from the well boring at Mr. L. Woolman's, at Atlantic City, 

 form the basis for the citation of the above species as a probable New 

 Jersey shell. I should coxisider the fragments as pertaining to two distinct 



