92 PALEONTOLOGY OF NEW JEESEY. 



but sloping quite gradually on the posterior side. Beaks moderately large, 

 somewhat projecting above the hinge and slightly incurved ; situated at 

 about the anterior third of the entire length of the valves. Cardinal area 

 moderate in size and extending about two-thirds of the length. Teeth un- 

 known. Surface as indicated on internal casts marked by radiating ribs, 

 pretty fine and numerous on the anterior end and in the mesial sulcus, be- 

 coming much coarser posteriorly, and showing a slight tendency to alter- 

 nation in size between the sulcus and posterior umbonal angle, and on the 

 cardinal slope a tendency to bifurcation in some cases. 



The species is not a very abundant one, but is sufficiently distinct to 

 be readily detected when found. It differs from C. iiniopsis Conrad, found in 

 the same beds, in being more prolonged behind, in the smaller mesial sulcus 

 coarser and more direct ribs and less quadrangular form. 



Formation and locality. — The only .examples which I have observed 

 from the State are from Freehold, N. J., and are from the Lower Green 

 Marls ; Dr. Morton's types having been found in Alabama, being not often 

 found at Prairie Bluff and vicinity. Mr. Gabb and Mr. Meek both cite it as 

 from New Jersey, but do not credit it to any other locality. 



Cibota uniopsis. 

 Plate XI, Ficrs. 32 and 33. 



Area uniopsis Conrad. J. A. K S., Phil., n. ser., Vol. II, p. 275, PL XXIY, Fig. 17 



Gabb Synop., p. 98. Meek, Checklist, p. 9. 

 A J uniopsis (Con.). M( ek, Geol. Surv. K J., 1868, p. 725. 



Shell rather above a medium size, transversely elongate, and trapezoidal 

 or subrhomboidal in outline, with moderately convex valves, which are 

 broadly sulcated in the middle, particularly on the right valve, and only 

 moderately elevated beaks, situated at about the anterior third of the length, 

 and which in the casts appear to have been scarcely enrolled and moderately 

 distant from each other. Hinge-line not quite as long as the body of the 

 shell, in the cast showing characters of a -rather low area; anterior end 

 obliquely rounded, receeding below ; basal line broadly sinuate and the 

 posterior end obliquely truncate, longest below the center. The surface 

 appears to have been marked only by slender radii, as none are preserved 

 on the casts. Muscular scars only faintly impressed. 



