156 ON THE NAIADES, 



injlatis, prope apices undulatis ; cicatricibus vix cernendis ; margaritd pulchrd et 

 iridescente. 



Shell subrotund, much inflated near the beaks, inequilateral, obtusely angular behind; 

 valves thin ; epidermis yellow, with numerous green rays ; beaks inflated, near the tip 

 undulated ; cicatrices scarcely perceptible ; nacre beautifully pearly and iridescent. 



Hab. China. W. W. Wood. 



My Cabinet. 

 Cabinet of the Academy of Natural Sciences of Philadelphia. 

 Cabinet of Mr Hyde. 

 Diam. 1-6, Length 2-3, Breadth 3'4 inches. 



Shell subrotund, much inflated in the region of the beaks, inequi- 

 lateral, connate before and behind the beaks, obtusely angular behind, 

 rounded before, posterior slope carinate ; substance of the shell thin ; 

 epidermis smooth, yellow with numerous beautiful green rays over the 

 whole disk, which are darker on the posterior part and obsolete on the 

 umbones ; ligament long and thin ; beaks inflated and terminated with 

 about six nearly parallel undulations ; teeth, none ; cicatrices scarcely 

 perceptible; cavity of the beaks shallow and rounded ; nacre beautifully 

 pearly and highly iridescent, sometimes tinged with salmon and pink. 



Remarks. — Several specimens of this species have been within a few 

 years received from Canton, and Mr Wood, to whom I owe one of 

 mine, informed me that he believes it to be a native of that country, and 

 most probably dwelling in the waters of the neighbourhood of Canton. 

 It is certainly among the most beautiful of the genus which has come 

 under my notice, and is remarkable for its great area, its inflation of 

 the region of the beaks, its smooth epidermis, its splendid rays and ex- 

 quisitely beautiful nacre, which no pencil can imitate. I have it of 

 several different ages — when very young it is less rotund, being some- 

 what trapezoidal, the dorsal margin nearly straight and the rays obso- 

 lete. The specimen figured is not half the size of the largest specimen 

 in my cabinet, but I have chosen it for its great perfection in having 

 the valves completely connate before and behind the beaks. 



