20 NEW UNIONIDiE, MELANIDiE, ETC., 



cicatrices distinct, large and well impressed ; posterior cicatrices confluent, large and 

 slightly impressed ; dorsal cicatrices placed over the centre of the cavity of the beaks ; 

 cavity of the shell deep and wide ; cavity of the beaks rather shallow and rounded ; 

 nacre white and iridescent. 



Remarks. — This is a small species which reminds us of parvus, Bar., but it has an 

 oblong outline, while parvus is elliptical. It is in outline near to modeshis, Fer., and 

 resembles it in color of the epidermis. It is, however, a larger and much more in- 

 flated species. It is also near to cicur, (nobis,) but is not so carinate and not so thin 

 a species. I have over a dozen specimens before me, diiferiug little in the outline or 

 size. The old female individuals are very much enlarged on the umbonial slope, 

 which gives a projection of the margin, and causes a slight emargination of the basal 

 margin. None of them were perfect enough in the beaks to observe the character of 

 the undulations of the tips. Some of the specimens are nearly cylindrical. 



Unio Gastonensis. pi. 6, fig. 18. 



Testa IsBvi, subelliptica, oompressa, valde insequilaterali, ad lutere planulata, postice vix biangulata, antice 

 rotunda ; valvulis crassiuseulis, antiee crassioribus ; natibus prominulis ; epidermide tenebroso-fusoa, 

 eradiata; dentibus cardinalibus parviusculis, in valvule sinistro tripartitibus j lateralibus longis, laiuel- 

 latis subcurvisque ; margarita purpurescente et iridescente. 



Shell smooth, subelliptical, compressed, very inequilateral, flattened at the sides, 

 scarcely biangular behind, round before; valves somewhat thick, thicker before; 

 beaks a little prominent: epidermis dark brown without rays ; cardinal teeth rather 

 small, tripartite in the left valve ; lateral teeth long, lamellar and somewhat curved ; 

 nacre pui'plish and iridescent. 



Proc. Acad. Nat. Sci., 1863, p. 191. 



Eah — Mine Creek, Gaston County, North Carolina, C. M. Wheatley. 



My cabinet and cabinet of Mr. Wheatley. 

 Diam. -9, Length 1*8, Breadth 3 inches. 



Shell smooth, subelliptical, compressed, very inequilateral, flattened at the sides, 

 nearly biangular behind, round before ; substance of the shell somewhat thick, thicker 

 before ; beaks slightly prominent ; ligament rather long, narrow and dark brown ; 

 epidermis dark brown, without rays and with rather proximate marks of growth ; 

 umbonial slope slightly raised and rounded ; posterior slope very narrow and carinate ; 

 cardinal teeth rather small, treble in the left and double in the right valve ; lateral 

 teeth long, lamellar and somewhat curved ; anterior cicatrices distinct, rather large, 

 well impressed ; posterior cicatrices confluent, large and slightly impressed ; dorsal 

 cicatrices placed immediately over the centre of the cavity of the beaks ; cavity of the 

 shell very shallow and wide ; cavity of the beaks very shallow and rounded ; nacre 

 purplish and iridescent. 



