246 PALEONTOLOGY OF NEW JEESEY. 



tively small; lateral moderately strong and but slightly curved. The 

 shells which I have identified with the above name are somewhat broader 

 or higher than the generality of specimens of U. radiatus as they occur in 

 the Hudson River and its tributaries; and the cardinal teeth are smaller or 

 more compressed. In other respects they correspond very closely in all 

 general particulars. There is very great difficulty in distinguishing be- 

 tween this and Z7. cariosoides. In fact I cannot say that I am at all sure I 

 have done so. Between their living representatives, if we take casts of the 

 interiors and throw out the additional convexity of U, cariosus, it would be 

 very difficult to say wherein they diff^er, and among these fossil specimens 

 there is not an individual but that is more or less distorted as well as other- 

 wise imperfect. 



Unio subrptundoides. 

 Plate XXXII, Fig. 5. 



Unio subrotimdoides La. Proc. A. N. Sci., Phil.^ 1868, p. 163. Pamphlet by Lea, p. 30. 



Of this species I have not been able to identify any individual among 

 the collections which I have examined and have therefore figured the type 

 specimen used in tlie original description, as labeled in the collection at 

 Philadelphia. The specimen is very broad ovate in outline, being longer 

 than high; the greatest height being considerably behind the beaks but 

 nearly midway of the length of the shell. Valves depressed convex with 

 strong concentric striae; hinge-line strongly arcuate and the beaks ap- 

 pressed; anterior end of shell short. Cardinal teethi Lateral teeth long, 

 thin, and strongly arched. 



Mr. Lea states in his description of this shell that the cardinal teeth are 

 '^apparently small." The space for the cardinal tooth in the specimen is 

 filled with foreign matter, but I think it would prove to be of considerable 

 dimensions if cleaned out. The form of the shell differs more from U, sub- 

 rotundiis Lea, as figured by that author in his ''Land and Fresh Water 

 Shells," Vol. IV, PI. 18, Fig. 45, than any other species of this group of 

 fossils differs from the one after which it was named. In fact it differs so 

 much that if left entirely to my own judgment I should not have thought 

 of referring it to that species at all. The measurements as given with Mr. 



