133 
PALAEONTOLOGY OF NEW-YORK. 
Chonetes lepida. 
PLATE XXI. 
Chonetes lepida : Hall in Tenth Report on the State Cabinet, p. 148. 1857. 
Shell small, scarcely transverse, semielliptical, subhemispherical : 
hinge-line about equalling the width of the shell below. 
Ventral valve more or less gibbous, with a longitudinal depression along 
the centre in well-marked specimens; curving abruptly to the front 
and sides, with cardinal angles scarcely flattened. 
Dorsal valve following the curvature 'of the opposite valve, with a lesser 
concavity. 
Area of the ventral valve narrow, distinctly wider in the middle, and 
sloping with a gentle curve to the cardinal angles. The foramen is 
small, partially closed by a pseudo-deltidium, and filled by the cardi¬ 
nal process of the opposite valve. The dorsal area is scarcely equal to 
the thickness of the shell. 
Surface marked by slender angular bifurcating striae, of which there 
are ten or twelve near the umbo and twice as many on the margin, 
and in some specimens a larger number. Two of the striae, on each side 
of the centre near the beak of the ventral valve, are larger and more 
prominent than the others : the space between them is depressed and 
occupied by two or three smaller striae, which are given off from the 
larger ones on each side. The larger striae are more prominent near 
the beak than on any other part of the valve, and. give an almost 
bicarinate aspect to the umbo, with a' distinct sinus which becomes 
obsolete near the base of the shell. 
The hinge-line usually shows two or three spines on each side of the 
centre; but in some individuals, the bases of five spines can be distinctly 
seen on each side of the beak. 
The interior of the dorsal valve shows a longitudinal depression, and 
the course of the striae is well defined and strongly papillose. 
The cardinal process has not been seen in its connexion with the 
dorsal valve. Some casts of the ventral valve show a gibbous centre, 
