FRESH WATER AND LAND SHELLS. H 



trices nearly in the centre of the cavity of the beaks, on the inferior posterior part of the 

 cardinal tooth; palleal cicatrices distinctly impressed; cavity of tiie shell shallow, cavity 

 of the beaks shallow and subangular; nacre white and iridescent. 



Remarks. — It is to be particularly regretted that a single specimen only of this species 

 should have been received from Dr. Gibbes. The cardinal teeth in both valves arc Irlparlilc. 

 They are distinctly divided into three lobes, of nearly equal size and form. This is so unique 

 that I have inserted it with some hesitation as a permanent character, tripartition being 

 so unprecedented. It may possibly be accidental. Should other specimens prove this 

 form to be persistent, this species will present an anomaly peculiarly its own. The lateral 

 teeth are, as usual, single in the right and double in the left valve; but the terminal in- 

 ferior portion is remarkably enlarged and thickened in the latter valve, so as to run 

 beyond the superior portion. The marginal portion of the disc is remarkably furnished 

 with imbricate epidermal matter. It has somewhat the outline of U. complanalus, but may 

 easily be distinguished from that species by its being more elevated in the beaks, in its 

 imbricate margin, and in the form of the teeth. 



Unio perstriatus. pi. XII. Fig. 3. 



7'esld leevi, valcle transi'ersci, valde compressd, subemars^inatd, vahle inxquUaterali, poslicc siibhiana:idutd; 

 valvuKs tenuibus ; tiatibus parvis,vix piominentibiis, ad apkem uiididatus ; epidcnnide luteo-fuscd,per!striat(i: 

 denlibus cardinalibus parvis, obliquis ; lateralibus prxlongis reciisqite; margurilu alba et irUescenle. 



Shell smooth, very transverse, very much compressed, subemarginate, very inequihiteral, subbiangular behind; 

 valves thin; beaks smal], scarcely prominent, undulated at the tip; epidermis yellowish-brown, verj- much 

 striated; cardinal teeth small, oblique; lateral teeth very long; and straight; nacre white and iridescent. 



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

 My cabinet and cabinet of Dr. Barratt. 

 Diam. .5, Length 1, Breadth 2.3 inches. 



Shell smooth, very transverse, very much compressed, slightly cmarginate, very inequi- 

 lateral, subbiangular behind, obtusely rounded before, posterior slope wide and flattened; 

 substance of the shell thin; beaks placed near to the anterior margin and furnished with 

 minute undulations at the tip, scarcely prominent, but rather pointed; ligament long and 

 thin; epidermis yellowish-brown, with numerous imbricate striffi covering nearly the 

 whole of the disks, and with only one or two distant marks of growth; umbonial slope 

 biangular and flattened; cardinal teeth small, oblique, double in the right and single in 

 the left valve; lateral teeth very long, straight and thickened at the posterior ends; 

 anterior cicatrices distinct; dorsal cicatrices placed under the plate between the cardinal 

 and lateral teeth; cavity of the shell exceedingly shallow; cavity of the beaks very shal- 

 low and rounded ; nacre white and iridescent. 



Remarks. — Dr. Barratt sent me four specimens of this species, which may easily be 

 distinguished by its peculiar striated epidermis, and its compressed form. It scarcely 

 belongs to that large group of which the U. complanalas is the type, but certainly borders 

 on it. The nacre of three of the specimens is white, slightly tinged with blur. The 

 fourtli specimen is |)urplish. The lines of growth arc very remarkable, being few and 



