f 



254 



directions: not dis- 

 tinctly defined umbo- 

 V n ;il slope; fineconcen- 



^ m trie lines, and irreg- 



^B ular concentric var- 

 ices. 



!9A. Nucula corbttliformis. Left valve, natural rOlllld 111 tlie Xitllll- 



size and enlarged ; right valve enlarged (after Hall). QtOIl "TOllD Oil the 



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

 Gems NUCULITES. Conrad. 



[Ety. : From Nucula, a genus; nucula, a little nut.] 

 (1841: Geol. Surv. N. Y. Ann. Rep't, p. 49.) 



Shells with equal inequilateral valves, longer than high; 

 with the anterior end rounded, 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. 



Nucdlites oblongatus. Conrad. (Fig. 170.) (Pal.N. Y., 

 Vol. V., Pt. L, p. 324, PI. XL VII.) 



Distinguishing Characters. — Elongate ovate outline, widest 

 ;it the anterior end: rounded umbonal ridge; strong vertical 

 clavicle, <>r (in the internal mold) its impression. 



Fio. 170. tfuculites oblongatus. Three internal molds, showing the impression of the 

 clavicle and the hinge crenulations (from Hallj. 



