JI06 
PALEONTOLOGY OF NEW-YORK. 
Meristella haskmsi. 
PLATE XLIX. 
Meristella haskinsi : Hall, Thirteenth Report on the State Cabinet, p. 84. 1860. 
Shell broadly ovate, more or less gibbous; length and breadth nearly 
equal, the greatest width anterior to the middle; slightly sinuate in 
front. In many well-formed specimens the length and width are about 
equal; when the length is greater, it is due to the extension of 
the beak of the ventral valve. 
Ventral valve regularly convex, often gibbous above the middle, and 
curving regularly to the sides and more gently to the front, which is 
sometimes a little impressed at the margin by a broad shallow sinus : 
beak elevated, slightly incurved and broadly truncated by a circular 
foramen. The triangular space beneath the apex is occupied by delti- 
dial plates, which appear to be closely anchylosed in the centre. 
Dorsal valve usually a little wider than long, moderately convex in 
young shells, gibbous in the middle and above in older specimens, 
curving regularly to the sides and front, and scarcely affected by the 
slight elevation near the anterior margin : beak short, and neatly 
incurved beneath the deltidial plates of the opposite valve. 
Surface marked by fine concentric strim, which are raised and thread¬ 
like, and sometimes crowded together in fascicles : these appear also 
to be indistinctly radiate or crenulate. In exfoliated specimens there 
are sometimes distinct radiating striae upon the surface. 
The rostral cavity of the ventral valve is narrow, the teeth are of 
moderate strength, and the dental plates reach the bottom of the cavity 
and extend forward ; the muscular area is broadly triangular and strongly 
striate. In the dorsal valve the muscular area is ovate or cordiform, and 
extends below the middle of the valve ; the low slender septum extends 
a little beyond the muscular area. 
This species is quite distinct, in its various phases, from the M. bcirrisi, which 
is more gibbous, with the ventral beak more closely incurved. In well-preserved 
