34 PALEONTOLOGY OF NEW JERSEY. 



ribs, much broader than the grooves on its opposite surface. Ligamental 

 pit in each valve large and deep. On a fragment of a convex valve, one of 

 the lateral ribs and its corresponding furrow measure barely less than 1| 

 inches on the margin of the valve. The young shells, at least the convex 

 valve, might readily be considered as a distinct species,- as from its great 

 rotundity and the very narrow grooves between the broad flattened ribs it 

 appears like an adult shell. 



Locality : The shell would appear to have been not very uncommon 

 in the marls near Shiloh, N. J. ; but among all those obtained no entire 

 valves have been seen except very small ones. I have specimens from the 

 collections at Rutgers College, New Brunswick; from the National Museum, 

 and from the Academy of Natural Sciences at Philadelphia. 



Family SPONDYLID^. 

 Genus SPONDYLUS Lamarck. 



Spondylus inornatus, n. sp. 



PL V, figs. 1 and 2. 



A single upper valve of either a young specimen or of a small species 

 of this genus is found among the collections from Shiloh, N. J. The valve 

 is subcircular in outline and depressed convex on the surface. It is com- 

 paratively free from ornamentation, having concentric lines of growth and 

 a somewhat obscurely scabrous surface, with a tendency to radiation in the 

 arrangement of the pustules. In the interior the hinge is well developed, 

 the teeth being moderately large and very divergent, but the ligamental 

 pit is quite small and obscure. The adductor muscular scar is subcentral, 

 and consists of two very broadly ovate scars of nearly equal size, the 

 outer overlapping the inner about one-third of its diameter. Lower valve 

 unknown. 



I know of no true Spondylus in the Atlantic Miocene beds; otherwise 

 I should have hesitated to designate this by name. The want of either true 

 rays or spines on this shell is its most conspicuous feature. 



Locality: Shiloh, N. J. From the collection of the National Museum. 



