rsEunonoN 1093 



rounded at and behind the middle ; posterior ridge very faintly, 

 widely double, ending at and below the median line in a wide, 

 faint biangulation ; dorsal slope rather abruptly subtruncate ; 

 surface pale chestnut, the epidermis subject to exfoliation; 

 teeth small ; nacre pale orange under the beaks, becoming rosy 

 white in the disk, iridescent and ornamented with feeble, trans- 

 verse striae. 



Length 53, height 32. diam. tq mm. 



Cambodia. 

 Psendodon tlwnisoni Morlet, Jl. de Conch., XXXII, 1884. p. 



40T, pi. xiTi, figs. 2, 2a. — Simpson, Syn., 1900, p. 838. 

 Margaritana ihomsoni P^TEL, Conch. Sam., Ill, 1890, p. 174. 



Morlet states that this shell has feeble laterals. I cannot 

 be certain that it is a Pseudodon. It is possibly a species of 

 Hyriopsis. 



Pseudodon salwenianus (Gould). 



Shell rhomboid elliptical, compressed or convex, subsolid, 

 inequilateral ; beaks only moderately elevated ; dorsal outline 

 lightly arcuate ; anterior end rounded ; base line lightly curved ; 

 posterior end oblic|uely truncate, joining the dorsal end with 

 an angle ; posterior ridge strongly and angularly developed ; 

 ending in a blunt point near the base ; dorsal slope radiately 

 plicate ; epidermis blackish ; muscle scars shallow ; nacre sub- 

 livid. 



Length 140, height 64, diam 31.5 mm. 



River Salwen, British Burma. 

 Anodon sahveniana Gould, Pr. Bost. Soc. N. Hist.. I, 1844.., 



p. t6o. 

 Anodonta sahveniana Gould. Otia Conch., 1862. p. 193. 

 Pseudodon sahveniana Conrad, Am. Jl. Conch., I. 1865, p. 

 . 233. 

 Monocondylcra sahveviana P.-jHEL, Conch. Sam., Ill, 1890. p. 



174. 

 Unio sahvenianus Sowkrby. Conch. Icon., X\'I. 1868, pi. 



xciv, fig. 513. 

 Margaron (Monocondylara) sahcveniana Lea, Syn., 1870, p. y2. 



