108 ON THE NAIADES, 



some years since by a dealer in Paris. It perhaps most resembles the 

 Zeylanica (Lamarck). It differs, however, in being more compressed, 

 more rotund, in having longer lateral teeth, and in these being serru- 

 late. The nacre is rather thinner, and is coloured. On comparison 

 it will be observed that the anterior tooth of the Zeylanica is merely 

 a tubercle, while that of rotunduta is long and lamellar. The nacre 

 is disposed to be pinkish on the posterior part. 



Cyrena Jayensis. Plate XVII. fis;. 52. 



»• 



Testa subrotunda, subxqtiilaterali, antice rugosd; valvulis crassis ; natibus par- 

 vis, elevatis ; dentibus cardinalibus bifidis, lateruUbus longis, minute serratis, 

 rectisque; margaritd purpurea. 



Shell subrotund, nearly equilateral, transversely wrinkled on the anterior part ; 

 valves rather thick ; beaks small, elevated ; cardinal teeth bifid ; lateral teeth long, 

 nearly straight, and minutely serrulate ; nacre purple. 



Hab. Batavia? J. C. Jay, M.D. 



My Cabinet. 

 Cabinet of Dr Jay. 

 Diam. 1-1, Length 2-2, Breadth 2-3 inches. 



Shell subrotund, nearly equilateral, furnished with transverse rather 

 large wrinkles on the anterior part; substance of the shell rather thick ; 

 beaks small, elevated, retuse ; ligament very short and thick ; epidermis 

 dark brown, shining; cardinal teeth bifid, long, nearly straight and 

 minutely serrulate ; cicatrices scarcely perceptible ; cavity of the shell 

 shallow; cavity of the beaks subangular; nacre dark purple, sometimes 

 whitish. 



Remarks. — It is to the kindness of Dr Jay I am indebted for the 

 specimen figured. That of his cabinet is rather more oblique than 

 this. The Jayensis has some resemblance to the rotundata, described 

 herein, but differs in having rather large wrinkles on the anterior part, 

 in having more elevated beaks, and in the dark purple colour of the 

 nacre. 



