CHIEFLY OF THE UNITED STATES. 285 



lateral teeth very long, oblique, lamellar and corrugate ; nacre wliite and very 



iridescent. 



Proc. Aoad. Nat. Sci. 1865, p. 75. 



^rt5._Cbina, A. R. Wright, M. D. 



My cabinet and cabinet of Buffalo Society of Natural History, New York. 

 Diam. *9, Length 1-3, Breadth 2'5 inches. 



Shell plicate, wide, inflated towards the beaks, very inequilateral, acutely angular 

 behind and rounded before ; substance of the shell rather thick, thicker before ; beaks 

 rather prominent, furnished with small corrugate folds, some of which assume an 

 angular form; ligament rather long, rather thick and light brown; epidermis dark 

 brown, without rays, with distant marks of growth and with a narrow border of 

 lighter brown ; umbonial slope obtusely angular ; posterior slope narrow-elliptic, 

 "with a few imperfect undulations; cardinal teeth rather long, somewhat oblique, 

 crenulate, lamellar and double in both valves; lateral teeth very long, oblique, lamel- 

 lar and corrugate ; anterior cicatrices distinct, rather lai'ge and well impressed; pos- 

 terior cicatrices confluent, rather large and slightly impressed ; dorsal cicatrices 

 placed above the centre of the cavity of the beaks; cavity of the shell wide and rather 

 deep ; cavity of the beaks rather deep and subangular ; nacre white and very irides- 

 cent. 



Remarlcs. — Two specimens of this species were sent for my examination by the 

 Buffalo Society of Natural History, New York. It belongs to the group of which 

 Marchisonianus (nobis) may be considered the type. It is more inflated, rather larger 

 and has a less number of undulations. It differs from Osbeckii, Phili. = Shanghai- 

 ensis (nobis) in being more oblique, and not being cylindrical. It reminds one of U. 

 Pazii (nobis), also from China, but that shell is not plicate and is more oblique. It 

 is, in outline, near to Dunherli (nobis) from New Granada, but that is a thinner and 

 more transverse shell, with the South American character of radiating folds, which 

 no Asiatic or North American species has, to my knowledge. In outline it is cer- 

 tainly very nearly the same as U. tumidus, Retz., common to most parts of Europe. 

 The description is made from a very perfect specimen. The second one is quite im- 

 perfect, being so much eroded as to be devoid of folds. It does not seem to possess 

 the light-colored epidermal margin, and this character maj' not be permanent. I 

 name it after Dr. Wright, who has deposited, in the cabinet of the Buffalo Society of 

 Natural History, a number of fine shells from the fresh waters of China, among which 

 is a gigantic specimen of U. Guining'd (nobis), being much larger than I supposed it 

 ever occurred. It has the following dimensions: Diameter 2 inches, length 5 J inches 

 and width 9j inches. The wing is entirely gone and the undulations towards the 

 beaks are nearly obliterated. 



