2.54 



directions; not dis- 

 tinctly defined unibo- 

 nal slope; fiiieconcen- 

 tric lines, and irrejj,- 

 ular concentric var- 

 ices. 



Found in the Ham- 

 ilton group, on tlie 

 shore of Lake Erie. (Coll. Am. Mus. Nat. Hist. New York.) 



Fig. 169A. Niicula corbnlifonnig. I>eft vah>'. natural 

 size and enlarged : right valve enlarged (after Hall). 



Genus NITULITES. Conrad. 



[Ety. : From Xi/cxbt. a genus; nucuhi, a little nut.] 

 (1841: Geol. Surv. ]S^. Y. Ann. Rep't, p. 49.) 



Shells with equal inequilateral valves, longer than high; 

 with the anterior end I'ouuded. and the posterior end some- 

 times obliquely truncate and pointed. The beaks are 

 anterior, and the cardinal line arcuate. The hinge bears a 

 row of transverse narrow teeth, which extend from the 

 anterior to the posterior muscular scar. The ligament is 

 external, a narrow groove serving as its receptacle. The 

 anterior muscular scar is separated from the shell by a 

 vertical, or slightly oblique, partition (clavicle). Surface 

 concentrically striate. 



NucuLiTES OBLoxGATUs. Courad. (Fig. 170.) (Pal.N.Y.. 

 Vol. v., Pt. I., p. 324. PI. XLVn.) 



Distinguishing Cliaracters. — Elongate ovate outline, widest 

 at the anterior end : rounded umbonal ridge ; strong vertical 

 clavicle, or (in the internal mold) its imjDression. 



Fig. 170. Nucidites oblongatus. Three internal molds, showing the impression of the 

 clavicle and the hinge crenulations (from Hall;. 



