34 PALEONTOLOGY OF NEW JERSEY. 
ribs, much broader than the grooves on its opposite surface. Ligamental 
pit in each valve large and deep. Ona fragment of a convex valve, one of 
the lateral ribs and its corresponding furrow measure barely less than 14 
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 SPONDYLID2. 
Genus SPONDYLUS Lamarck. 
SPONDYLUS INORNATUS, 0. 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. 
