48 ON THE NAIADES, 



spherical, the other is gibbous. The posterior slope of the young 

 specimen is decorated with six distinct green rays, there being three 

 on each valve. 



Anodonta palna. Plate VII. fig. 18. 



Testa suhovatCi, hixqiiilaterali, subcompressa ; valvulis subcrassis ; epidermide 

 oUvaced et obsolete radiatd ; natibus prominentibus ; apicibiis granidatis ; cica- 

 iricibus perspicuis ; margaritd alba ; sed in natiuni cavo interdum colore salmo- 

 ?iis tincid. 



Shell subovate, inequilateral, rather compressed ; valves somewhat thick; epidermis 

 olive with obsolete rays ; beaks prominent and granulate at tip ; cicatrices perceptible ; 

 nacre white, sometimes salmon in the cavity of the beaks. 



Hab. Bear Grass Creek, near Louisville. Mr T. H. Taylor. 



My Cabinet. 



Cabinet of the Academy of Natural Sciences of Philadelphia. 



Cabinet of Mr Ronaldson. 



Diam. 2-3, Length 3-1, Breadth 5*6 inches. 



Shell subovate, inequilateral, rather compressed, subangular behind ; 



dorsal line slightly curved; substance of the shell thick; epidermis 



smooth, olive to dark green, brighter on the beaks; rays obsolete; 



ligament long and thick ; beaks elevated, granulate at tip ; cicatrices 



perceptible ; cavity of the beaks rather deep and rounded ; cavity of 



the disk somewhat flattened ; nacre white, sometimes salmon coloured 



in and about the cavity of the beaks. 



Bemarks. — This species of Anodonta offers quite a large area in 

 the circumference of the disk. Some specimens are, however, more 

 transverse than the one here described. It has a predisposition to 

 salmon colour in the region of the cavity of the beaks, and this is 

 sometimes of a very deep tint. The colour is irregularly distributed, 

 sometimes quite in spots, and a roughness, apparently a disease, often 

 accompanies it and produces a carious state of the nacre. It perhaps 

 most closely resembles the ^. catarada (Say) ; but is usually less in- 

 flated, is thicker in the substance of the shell, and less transverse. 



