E. Billings—New Species of Paleozoic Fossils. 357 
3. O. ceelata Hall, = Orbicula coelata, op. cit. p. 290, pl. 79, fig. 
9. Occurs at Troy. 
@, TD. Sp. 
saeaulied: Billings; has been found as yet only at the 
Straits of Belle Isle. 
The following are new species : 
. gemma.—Shell very small, about two or three lines in 
length, ovate, both valves moderately convex and_ nearly 
smooth. Ventral valve ovate, the anterior margin broadl 
rounded, with sometimes a portion in the middle nearly straight ; 
greatest width at about one-third the length from the front, 
thence tapering with gently convex or nearly straight sides to 
the beak, which is acutely rounded. The area is about one- 
Oe 
om deep groove, which extends to the apex of the beak. 
orsal valve is nearly circular, obscurely angular at the 
beak, and rather more broadly rounded at the front margin 
than at the sides. 
In the interior of the ventral valve there are two small mus- 
cular impressions of a lunate form, close to the cardinal margin, 
one on each side of the median line. A second pair consists of 
two elongate sub-linear scars, which extend from the posterior 
third of the length of the shell to points situated at about one- 
fourth the length from the front margin. These scars are nearly 
straight, parallel or slightly diverging forward, and divide the 
shell longitudinally into three nearly equal portions. Between 
them, about the ‘middle of the shell, are two other small 
obscurely defined impressions. There is also a small pit close 
_ to the hinge line and in the median line of the shell. In the 
interior of the dorsal valve there is an obscure rounded ridge 
which runs from the beak along the median line almost to the 
front margin. Close to the hinge line there is a pair of sma 
Scars, one on each side of the ridge. The other impressions in 
this valve have not been m t. 
e surface of both valves is in general nearly smooth, but 
when well preserved shows some obscure concentric strive. 
This species is closely allied to O. chromatica, the species on 
which the genus was founded, only differing from it, so far as 
the external characters are concerned, in being much smaller, 
and the beak of the ventral valve more extended. 
ee at Bic and St. Simon. Collected by T. C. Weston. 
smooth, but 
With fine concentric striz, Length seven lines, width a little 
