34 ON THE NAIADES, 



plicated; cardinal teeth double in both valves; lateral teeth straight; nacre splendidly 

 pearly, slightly salmon coloured, and beautifully iridescent. 



Hab. China. Mrs Murchison. 



My Cabinet. 

 Diam. -7, Length -8, Breadth 1-9 inches. 



Shell narrow-elliptical, transverse, inequilateral, angular behind, and 

 slightly emarginate at basal margin ; substance of the shell rather thin ; 

 beaks and umbones beautifully plicated ; umbonial slope subcarinate 

 and rough with the angles of the folds ; posterior slope finely plicate ; 

 ligament yellow and narrow; epidermis dark green; cardinal teeth 

 double in both valves ; lateral teeth straight ; anterior cicatrices distinct ; 

 posterior cicatrices confluent; dorsal cicatrices in the centre of the 

 cavity of the beaks ; cavity of the beaks shallow ; nacre rich, and splen- 

 didly pearly, slightly salmon coloured, and beautifully iridescent. 



Remarks. — This splendid species I owe to the great kindness of 

 Mrs Murchison, the wife of the present learned president of the Geo- 

 logical Society of London. Among many fine and rare shells received 

 from her I found this, which appears not to have been before de- 

 scribed. It perhaps most resembles the U. coeruleus (nobis), particu- 

 larly in the outline : it is, however, rather more transverse. It differs 

 greatly from the coeruleus in the number and size of the folds. These, 

 behind the umbonial slope, are parallel to the ligament ; while those on 

 the anterior margin are oblique. The acute angles formed by the 

 folds on the umbonial slope are very remarkable. The inferior part 

 of the shell is free from folds: this may not, however, prove a constant 

 character. Its nacre is without exception finer than any I have ever 

 seen, and rich beyond description. The folds being visible from the 

 interior, add greatly to its lustre.* 



* Since writing these remarks I have seen several specimens of this shell in Europe. At 

 the Jardin des Plantes, Monsieur de Blainville showed me two or three specimens recently 

 received, and not yet placed in the cabinet. He considered the shell undescribed, until I 

 mentioned the name I had given it. 



