56 PALAEONTOLOGY OF NEW JEE8EY. 



Genus NEITHEA Drouet. 



Neithea quinquecostata. 

 Plite VIII, Figs. 12-14. 



Peoten quinquecostata (Sowerby). Morton, Synop., p. 57, PI. XIX, Fig. 1. 



Janira Mortoni (D'Orb.). Prodr., p. 253. 



j^eithea Mortoni (D'Orb.). Gabb, Synops., Cret. Form., p. 149. Meek, Check-list 



Smith. Inst, p. 7. Geol. Surv. N. Jers., 1868, p. 725. 

 Vola Mortoni (D'Orb.), Stoliczka, Pal. Indica, Vol. Ill, p. 430. 

 Fcctcn quinquecostatus and P. quadricostatus of authors. 



Shell broadly ovate exclusive of the auriculations, and plano-convex to 

 concavo-convex in profile, right valve strongly convex, with a sharp, arching, 

 and incurved beak extending beyond and partially overarching the hinge- 

 line; hinge- line straight or nearly so, slightly declining on the anterior side; 

 nearly two -thirds as long as the entire, width of the shell; auriculations 

 moderate in size, the anterior one th^ smallest and constricted below where 

 it joins the body of the shell, forming a slight byssal notch; posterior side 

 triangular, longest at the hinge-line and receding below. Sides of the valve 

 where it joins the auriculations strongly incurved laterally, so as to cause the 

 sides to overhang. Valve marked by six strong, rounded, principal radiat- 

 ing costae, with from two to four smaller ones between. These are usually 

 distributed in the following maiiner: three between the two anterior strong 

 ones; three or four between the two antero-basal and median ones; three 

 usually between the postero-basal pair, and usually two only between the 

 posterior pair. There are also three or four anterior to the first strong ray, 

 and from four to six on the area posterior to the last principal ray. The 

 auriculations are also rayed, unequally on the opposite sides, the posterior 

 one most strongly. The characters of the flat or left valve have not been 

 observed on the New Jersey specimens. The casts, the only condition in 

 which I have seen them from within the State, show evidence of moderately 

 strong concentric lines crossing the rays and intermediate portions of the 

 shell. 



The shell seems to be subject to considerable variation in the number 

 and strength of the secondary costse, and this fact has given great latitude 

 to species-making, consequently we have several names under which the 



