74 BULLETIN OF THE LABORATORIES 



Allorismfi coiive.va, sp. n. 

 (Plate XII, Fig. 27.) 



Shell of medium size, quite tumid, with parallel margins and nu- 

 merous fine strise. Length nearly 2j4 times the height; hinge and 

 lower margins parallel and of equal length ; lower margin abruptly 

 rounded to the middle of the height, passing sharply into the concave 

 antero-dorsal line; lunette well defined; posterior margin broadly 

 rounded with slight angulation at the termini of two faint ridges be- 

 tween the post-umbonal ridge and the hinge; surface highest near the 

 middle, flattened postero-dorsally ; post umbonal ridge faint, the supra- 

 umbonal ridges inconspicuous, but producing slight deviation in the 

 numerous and regular concentric strias. The cast shows a long cardi- 

 nal groove. This shell is some respects a miniature of A. nobilis, but 

 is much more convex. The radiating strias characteristic of Allorisma 

 may be detected upon the cast. From A. winchelli, which it exactly 

 resembles in size, it may be distinguished by the parallel sides and the 

 form of the posterior margin. From all other forms of this age it will 

 readily be distinguished. Length 57 mm ; height 23 mm ; beak from 

 the front 10 mm ; convexity of both valves about 15 mm. Free-stone 

 layers of middle Waverly^ 6 miles northwest of Gyanville. Collected 

 by W. F. Cooper. 



Macrodon ? ? trlaii^nlfiris, sp- "• 

 (Plate VIII, Fig. 8.) 



A single right valve differs so from all associated forms that very 

 little idea is afforded of its relations. 



Shell thick, nuculiform, large; oudine subtriangular, beaks rather 

 prominent, somewhat incurved; hinge apparently flexed at nearly a 

 right angle at the beak, anterior margin nearly straight, meeting the 

 gently curved lower margin by an abrupt curve; posterior margin 

 very short, forming an acute angle with the lower margin and a very 

 obtuse one with the curved hinge line; post umbonal slope narrow, 

 inclined to the general surface of the valve at nearly a right angle ; 

 .surface marked by concentric striae and folds ; greatest convexity 



