FRESH WATER AND LAND SHELLS. 15 



margin; ligament sliort and tliick; epidermis dark-brown or black, roughly striate on the 

 margin, but smooth and highly polished on tiie sides and towards the beaks; marks of 

 growth rather indistinct and distant; umbonial slope rounded; cardinal teeth large, ele- 

 vated, crenulated, pointed, single in the right and double in the left valve; lateral teeth 

 lontT, rather thick, somewhat curved and separated from the cardinal tooth ; anterior cica- 

 trices distinct; posterior cicatrices distinct; dorsal cicatrices placed nearly in the centre 

 of the cavity of the beaks; cavity of the shell rather deep; cavity of the beaks shallow 

 and rounded; nacre usually salmon coloured, sometimes white. 



Remarks. — Many of this species were sent to me by Mr. White. None of the 

 beaks are sufficiently perfect to detect the undulations of the tips. The form and size of 

 this species approaches closely to U. confertus and JJ. Geddingsianus, (Nobis.) It may 

 be distincuished from them, however, by the remarkable polish of the superior portion of 

 the disk and the beaks, and by the rough stria? of the other portion of the epidermis. 

 The adult specimens are all very dark-brown or black. The younger shells are yellowish, 

 with numerous dark-green rays over nearly the whole disk. Some of the adult specimens 

 are quite straight on the basal margin, and almost falcate. 



Unio Lazarus. PI. XIV. Fig. 9. 



Testa Ixvi, arciiald, vahle Iransversci, compressci,vakU inxquilateruli, postice sitbbitingiila/ii ; valvulis pcr- 

 tcnuibits; nalibiis itndulatis, vix proininen/ibun; eindermide tenebroso-fusca, rugoso-striatu ; dmtlbus cardi- 

 nalibiis minimis; lateralibus longis, acicvlaris, remotis reclisque; murgaritc't vel alba vcl purpurea et valde 

 iridescent e. 



Shell smooth, arcuate, very wide, compressed, very inequilateral; subbiangular behind; valves very thin; 

 beaks undulated, scarcely prominent; epidermis dark-brown, roughly striate; cardinal teelh very small; lateral 

 teeth long, acicular, remote and straight; nacre white or purple and very iridescent. 



Hab. Abbeville District, S. C. J. P. Barratt, M. D. 

 My cabinet and cabinet of Dr. Barratt. 

 Diara. .4, Length .9, Breadth 2 inches. 



Shell smooth, emarginate at base, very wide, compressed, very inequilateral, behind 

 subbiangular, before rounded; posterior slope wide and flattened; substance of the shell 

 very thin, thicker before; beaks placed near to the anterior margin, furnished with very 

 minute undulations at the tip, scarcely prominent and very small; ligament long and thin; 

 epidermis dark-brown, roughly striate, with obscure marks of growth; umbonial slope 

 biangular; cardinal teeth very small, crenulate, double in the left and single in the right 

 valve; lateral teeth long, separated from the cardinal tooth, acicular, straight and slightly 

 turned up at the extreme posterior point; anterior cicatrices distinct; posterior cicatrices 

 confluent; dorsal cicatrices small and placed under the plate posterior to the cardinal 

 tooth; cavity of the shell very shallow; cavity of the beaks very shallow and rounded; 

 nacre white or purple. 



Remarks. — This is a small, very thin and fragile species. The young have very much 

 the appearance of the yoimg of the elongate variety of U. complanatus, but the adult 

 and middle aged are arcuate, and cannot be mistaken for that species. The young arc 



