346 PALEOZOIC PALEONTOLOGY. 
is in the condition of internal casts of the pedicle valve, upon which 
the cast of the flabellate muscular impression and the punctate sur- 
face are always conspicuous characters. ; 
LEPTAENA RHOMBOIDALIS (Wilck.) var. VENTRICOSA (Hall). 
Plate XLVI., Fig. 1. 
1859. Strophomena rugosa var. ventricosa Hall, Pal. N. Y., vol. IIL, 
p. 417, pl. 94, figs. 2 ef, 3. 
The variety of this cosmopolitan species, which occurs in the 
Oriskany beds, differs markedly from its earlier representatives in the 
“New Jersey faunas. 'The pedicle valve is more or less strongly convex 
toward the beak, not conspicuously flattened, as is the condition of 
the more usual members of the species, and because of this convexity 
posteriorly, the valve does not have the usual geniculation toward the 
front, but is strongly convex or gibbous. The concentric wrinkles are 
also much stronger, broader and further apart on these Oriskany speci- 
mens, giving to the shell altogether a different appearance than the 
typical form of the species. The brachial valve is strongly concave 
and is much more coarsely marked than is usually the case in the 
typical form of the species. 
This shell is quite generally distributed in the Oriskany beds of 
New Jersey, but has never been observed in great abundance and is 
always imperfectly preserved. It sometimes attains a great size, one 
individual having a length of 55 mm.; this size, however, is ex- 
ceptional. 
HIPPARIONYX PROXIMUS (Van.). 
Plate XLV., Fig. 12. 
1859. Orthis hipparionyx Hall, Pal. N. Y., vol. III., p. 407, pl. 89, 
figs. 1-4, pl. 90, figs. 1-7, pl. 91, figs. 4-5, pl. 94, fig. 4. 
Description.—Shell subcircular to subsemi-elliptical in outline; 
hinge-line shorter than the greatest width. Pedicle valve depressed- 
convex near the beak, flattened or slightly concave toward the lateral 
