OF DENISON UNIVERSITY. r, 



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 stric-e. 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 .\. amplus. 

 It is quite flat and almost destitute of markings. The anterior car 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 know;, 

 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 stria; are even more pronounced 

 than in the above, but the striae are apparently higher and are crossed 

 by innumerable very fine concentric s'.riiP. In some respects this form 

 resembles A. crenistriatus. 



Aulcidopecteii cooperi, sp. n. 

 (Plate XII, Figs. 16-17.) 



A beautiful species, found too late for careful study, diflers from 

 all others from the Ohio Waverly in its markings. Closely agreeing 

 with A. sub-cardifonnis. Her., in outline, but much less convex. 

 Left valve somewhat longer than wide, j)osterior 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 slriii;, crossing 

 shallow concentric folds; about 4 of the radiating striae occupy the 

 space of I mm ; anterior ear not seen. A fragment of whit seems lo 

 be the right valve of the same species accompanies it. This valve is 

 less convex and is marked only by very fine concentric strife, except 

 upon the posterior wing, which has the form and markings of that of 

 the left valve ; anterior wing Iopl'. n< iitc. srpnratcfi from the Ixxlv by 



