OF UENFSON UNIVEKSITV. 



incurved into the cavity belou- the deltidial phtes. Surface concen- 

 trically striate* with crowded lamelliform ridges toward the sides and 

 front." 



Length of our largest specimens nearly 30 mm, width 27 mm. 

 Varying greatly in form and size. The casts figured on Plate V give 

 a good idea of the vascular markings. 



Freestone of middle Waverly. Typical specimens arc from the 

 Chemung of New Vork. 



Centronrlhi juJid, Win. 

 (Plate II, Fig. 5.) 



Shell small, lenticular, ovate or somewhat transverse in outline ; 

 valve moderately convex, its beak covered by the higher, incurved 

 beak of the more convex ventral valve ; are i ib.sent. Surface marked 

 by concentric lines of growth and radiating lines (impressed from the 

 interior upon the cast ?) Internal characters of die genu^. 



Many specimens of this species may be found m the freestone 

 overlying shales above congl. II, at Newark and eastward. It agrees 

 in external feature perfectly with Prof. Hall's figures of this species. 

 Other forms are illustrated in figures 4 and 8 of Plate II, and may be 

 refered to this genus. As, however, we know nothing of the essen- 

 tial characters we may forbear burdening synonomv uith meaningless 

 names. 



(Plate II, Fig. I.) 



Some doubt attends the identification, on account of the condition 

 of our specimens, but Prof. Winchell was good enough to compare 

 our casts with the types and considers the identif.caiion as a proba- 

 ble one. 



.Ifhi/ris I((nn//(>s(i, I.cveil. 



(Plate II, Fig. 7.) 



The suecimens figured are from the layer below congl. I, and wc 



