OF DENISON UNIVERSITY. 
51 
From this species our left valve differs in the form of the anteri- 
or ear, which is less projecting. The posterior ear is broken, but evi- 
dently is very slightly defined. The valve is quite flat and is marked 
by distant, irregular and somewhat alternating striae. The surface 
markings are poorly preserved in our cast. 
A faint impression of the right valve of apparently the same spe- 
cies closely resembles in ascertainable characters that of A. amplus. 
It is quite flat and almost destitute of markings. The anterior ear is 
evidently very distinct from the body and separated from it by a deep 
bvssal sinus. The posterior ear is minute and ill-defined. Length of 
left valve 77 mm; width 81 mm ; hinge 53 mm.? Length of right 
valve 48 mm. This species occurs in some hitherto unidentified hori- 
zon evidently of the Freestone of middle or upper Waverly. 
In this connection should be mentioned a large species known 
only from a single fragment secured near the very top of the Waverly 
(ten feet below coal-measure congl.) 8 miles east of Newark. This 
fragment (Plate XII, Fig. 21) is nearly as large as the above but, if a 
left valve, as seems probable, must be very dissimilar in outline. The 
alternation and irregularity of the striae are even more pronounced 
than in the above, but the striae are apparently higher and are crossed 
by innumerable very fine concentric striae. In some respects this form 
resembles A. crenistriatus. 
Aviculopecten cooperi, sp. n. 
(Plate XII, Figs. 16-17.) 
A beautiful species, found too late for careful study, dilfers from 
all others from the Ohio Waverly in its markings. Closely agreeing 
with A. sub-cardiforrnis, Her., in outline, but much less convex. 
Left valve somewhat longer than wide, posterior ear of moderate size, 
not sharply set off from the body ; surface of valve and ear covered 
by very fine, rather uniform, but irregularly waved striae, crossing 
shallow concentric folds; about 4 of the radiating striae occupy the 
space of I mm ; anterior ear not seen. A fragment of what seems to 
be the right valve of the same species accompanies it. This valve is 
less convex and is marked only by very fine concentric striae, except 
upon the posterior wing, which has the form and markings of that of 
the left valve ; anterior wing long, acute, separated from the body by 
