NATURAL SCIENCES OF PHILADELPHIA. 163 



fresh-water shells have been found abundant; I mean of course the Wealden 

 of England, in which the distinguished geologist Dr. Mantell had worked so 

 successfully, and iu which he found the Iguanodon ManteUi, a gigantic terres- 

 trial reptile, and other animals, together with many fresh-water molluscs, par- 

 ticularly a large number of Uniomdie, analogous in form to these now so 

 happily found by Prof. Cope in this bed below the Green Sand* 



1 ought to state, iu connection with this subject, that Dr. Hayden published 

 with Mr. Meek, some ten years since, observations made by the former regard- 

 ing the estuary and fresh-water deposits near the mouth of the Judith River, 

 where Dr. Hajden found Uniones, Faludinie, &c. These geologists, considering 

 it the lowest, have called this number one. They say in their paper, published 

 in our Proceedings May, 1857, that " the estuarj- and fresh-water deposits at 

 the mouth of the Judith River are probably in a parallel with the lowest bed 

 of the great Lignite basin, though some portions of them may be somewhat 

 older." 



Uxio NASUToiDES.f — Shell smooth, very wide, compressed, very inequilateral, 

 biangular behind, rounded before ; beaks slightly raised, nearly terminal ; 

 cardinal teeth short and striate ; lateral teeth long, and nearly straight. 



Length 1-5 inches, breadth 4-6 inches. 



Remarks. — This species is very nearly the same in outline with the well- 

 known nasutits, Say, but it is more acute at the posterior margin, in which 

 character it is more nearly allied to Fisherianus (nobis). 



Unio radiatoides. — Shell smooth, regularly elliptical, compressed, inequi- 

 lateral, subangular behind and rounded before ; beaks slightly raised, subme- 

 dial ; cardinal teeth large; lateral teeth large, rather long and lamellar. 



Length 2-4 inches, breadth 4-3 inches. 



Remarks. — Some of the large and compressed varieties of radiatus, Lam., are 

 nearly of the same outline with this species, and the beaks are nearly iu the 

 same position. It is evidently a species of thickness and weight. 



L^Nio suBROTUNDoiDES. — Shell smooth, subrotund, very ranch compressed, 

 very inequilateral, rounded behind and before ; beaks slightly raised, nearly 

 terminal ; cardinal teeth apparently small ; lateral teeth long, lamellar and 

 arched. 



Length 2*6, breadth 3-4 inches. 



Remarks. — Very nearly of the same outline with subroiundus nobis, but not so 

 high in the beaks. The lateral teeth seem to be unusually long and curved. 



Unio carriosoides. — Shell smooth, broadly elliptical, somewhat inflated, ob- 

 tusely angular behind, rounded before ; beaks somewhat raised, removed from 

 medial ; cardinal teeth ; lateral teeth long and slightly curved. 



Length 2-5, breadth 4-8 inches. 



Remarks. — This is evidently a very regularly formed species, the curves be- 

 ing gentle and pleasing. It resembles iu outline some of the more transverse 

 large males of carriosus, Say. 



Unio humerosoides. — Shell smooth, ovately oblong, very much compressed, 

 rounded behind and before ; beaks slightly raised, removed from medial ; car- 

 dinal teeth large and compressed ; lateral teeth rather long and slightly curved. 



Length 2-6, breadth 4-2 inches. 



* While in London in 1852, my friend Dr. Mantell consulted me in relation to these 

 rnionidie from the VVealdon, of which he had several hundred specimens, with the inten- 

 tion of publishing them. For this purpose I grouped the whole of this fine collection, 

 and assimilated them to those of our existing western species. Owing to severe illness, 

 from which he never recovered, Dr Mantell did not publish these shells, and his collection 

 was dispersed by a public sale. On my return from the continent to London, fifteen 

 months afterward, I found in the cabinet of the late distinguished geologist, Mr. Sharp, a 

 portion of them, which he had purchased, and which still had the labels which I had 

 written for Dr. Mantell. I am not aware of any ol these having been published. 



t These descriptions are of course imperfect, being little more than from casts. Speci- 

 mens of all the species are deposited in the cabinet of the Academy of Natural Sciences. 



1868.] 



