28 
BULLETIN OF THE LABORATORIES 
Crenipecten Foerstii, sp. n. 
(Plate III, Fig. 9, 9a.) 
The species figured is, next to Entolium aviculatum, the most 
common bivalve at Flint Ridge, and finds its counterpart in Streblop- 
teria (?) tenuilineata, M. and W, Indeed, it is riot improbable that 
the two are identical, in spite of marked points of divergence. 
It would be impossible to reconcile the description of that 
species with our specimens, while Meek’s drawings are equally 
different. The reference to Streblopteria is certainly erroneous, 
although it is fair to add that Meek and Worthen had not 
seen the hinge. ‘ The genus Crenipecten, as defined by Hall, 
includes a diversity of forms ranging from such symetrical, long- 
hinged species as C. Winchelli to those oblique species represent- 
ed by C. amplus.and our own. A single specimen (Fig. 9 a.) from 
Mr. Foerste’s collection, gave evidence of the crenulated hinge area, 
from the impression, the shell having been exfoliated. The characters 
of Streblopteria are as follows : 
“Shell ovate or rounded, obliquely extended towards the anterior 
side; posterior wing broad, undefined, nearly rectangular, extending 
nearly as far as the posterior margin of the shell; anterior ear small, 
deeply defined; surface smooth or radiately ridged; one large, faintly 
marked, muscular impression a little behind the middle; one short, 
narrow tooth slightly diverging from the hinge on the posterior side of 
the beaks ; ligament confined to a narrow, simple facet on the hinge 
margin.” .. , 
In comparing our specimens with the figure of S. tenuilineatus 
we find, aside from its greater average size and different markings, that 
the anterior margin is more produced, and the anterior ear is much 
more sharply defined. There is little doubt that the two forms are at 
least congeneric. 
Shell below the ears subcircular, but moderately convex, equi- 
valve. Right valve with the anterior ear produced, rounded in front, 
separated from the valve by a deeply impressed, concave auricular 
sinus; posterior ear nearly rectangular, slightly concave in posterior 
outline, separated from the valve by an impressed line ; hinge line one 
half the height of the valves. Left valve of same form, but the ears 
less distinctly separated; hinge line less than half the height, anterior 
ear with concave front outline,. The beaks are acute and moderately 
