60 PALiEOJfTOLOGY OF NEW JERSEY. 



nal area existing. The interior of the valve is strongly marked by moder- 

 ately fine striae or ribs, which are flattened on their surfaces ; muscular 

 imprints not observable. Upper valve verj^ ventricose and strongly arcuate, 

 the beak thin and sharply incurved. Hinge open as in the lower valve, the 

 cardinal angles spread outward in the form of auriculations to meet those 

 of the opposite valve. The sides of the valve are sharply bent inward on 

 a line from the beak to the point of greatest width, forming a hiatus on 

 each side between the bpdy of the valve and the auriculation, as in the 

 genus Janira. Surface of the valve marked by strong, closely compact, 

 radiating ribs; every fifth or sixth one of which is stronger than the others, 

 and bears short, sharp, curved spines, some of whicli are nearly one-fourth 

 of an inch long, Avhile the others are only rugose fi-om the concentric 

 lamella which cross them. On the depressed spaces on the sides of the 

 valve there are no radii, the concentric lines only being present. Substance 

 of the shell thin in the cardinal portions and much thickened toward the 

 front. Interior of the valve marked by the radii, and the thickened front 

 margin strongly crenulate. 



A single highly decomposed specimen of Spondylus-like shell, in the 

 collection of the Academy of Natural Sciences, Philadelphia, may possi- 

 bly belong to this species, but its condition is such that its specific relations 

 are not determinable, and in a short time more it will have crumbled. It 

 shows no evidence of having been attached, however; the lower valve is 

 moderately convex and the upper one rather more ventricose; the area or 

 cardinal parts of both valves are beyond description, but the valves are 

 both marked by I'ays and spines, as are the upper valves of this one. It 

 may possibly represent an undescribed form, but looks like a specimen of 

 the D. echinata that had been entirely free except perhaps in its earlier 

 stages of growth. 



Formation and locality. — In the Lower Green Marls at Holmdel, Free- 

 hold, and on Mr. Woodward's farm, Monmouth County, New Jersey. It 

 does not seem to be abundant anywhere, and so far I have never seen a 

 perfect upper valve of even medium size. The imperfect upper valve figured 

 is from the collection of the Academy of Natural Sciences, Philadelphia, 

 and is without locality further than " N. Jersey." 



