OF DENISON UNIVERSITY. 
19 
Surface of both valves covered by minute, numerous regular striae up- 
on a plane surface ; toward the front the striae may become irregular 
and similar to the usual markings in the genus ; there are also traces 
of radiating grooves. The striae are much finer and less numerous 
than in L. ' scotica. Our specimens exceed in the closeness of the stri^ 
the example figured by Meek. Length of dorsal valve, 20 mm., 
width of same valve, 19 mm. 
Blue shale above conglomerate II, Newark, O. 
ORBICULOIDEA PLEURITES, Meek. 
(Plate III, Fig. 5, also vol. Ill, Plate VIII, Figs. 13, 14.) 
Shell large, plano-convex, elliptical, s Ventral valve in perfect 
specimens nearly a true ellipse or slightly oval, strongly convex, great- 
est elevation near the middle, beak sub-terminal or terminal, depressed, 
length to width as 25 to 22, surface marked by numerous, rather strong 
concentric lines which may be quite irregular. Dorsal or under valve 
flat or slightly concave with strictly concentric striae and marked by a 
deep oval impression, which extends one-third the diameter of the 
shell. Length of a large specimen, 25 mm., width, 22 mm., height, 
45 mm. 
It was long suspected that the large dorsal valves associated with 
O. pleurites were of that species before the discovery of two valves in 
opposition settled the matter. 
Shale above congl. II, Newark and the same horizon near Gann, 
Knox Co. 
PODUCTUS RARICOSTATUS, Sp. n. 
(Plate III, Fig. 1.9 ; Vol. Ill, Plate III, Fig. 28, ?) 
Ventral valve of nearly the size and proportions of P. newberryi 
in its smaller forms known as P. annosa. Sub-quadrate, with regular- 
ly arching surface and acutely pointed somewhat projecting and in- 
curved beak, angles acute, sub-elevated, mesial depression slight or 
none; marked by distant rounded irregular ribs, fine numerous concen- 
tric striae and variable concentric grooves; spines few, scattered. Dorsal 
valve apparently the same as in the last volume figured as possibly P. 
lachrymosus var ; suface plane to a short distance from the margin 
where rather suddenly reflexed to correspond with the opposite valve, 
