I 092 ■ PSEUDODON 



Monocondylus tumidus INIorelet, Jl. de Conch., XIV, 1866, 



p. 62. — Mabii.le. Rev. Zool., XXIII, 1872, p. SL pi. v, figs. 



6, 7. 

 Pscndodon tumidus Morelet. Ser. Conch., W , 1875, P- v337' 



pi. XVI, fig. I. — Simpson, Syn., 1900, p. 837. 



There is an old, somewhat eroded, dead shell in the Lea 

 collection from Haines labelled Monocondylcca inoscularis, 

 Siam, which is not Gould's species I am sure, but may be the 

 above. It is no millimeters in length. 70 in height and 45 in 

 diameter. The earlier growth lines conform to those of More- 

 let's shell, but in the later ones the posterior point is somewhat 

 drawn down, as is often the case with old shells. The species 

 may be distinguished from allied forms by its inflation, its 

 nearly elliptical form and the high, narrow posterior ridges. 



Pseudodox ovalis Morlet. 



Shell elliptic rhomboid, rather short, subcompressed, thin, 

 inequilateral ; beaks low ; posterior ridge full, widely rounded, 

 ending bluntly behind, a little above the base ; anterior end very 

 slightly narrowed, rounded ; base line evenly curved ; dorsal 

 outline curved, produced into a low wing behind ; dorsal slope 

 obliquely subtruncate ; epidermis with decided, concentric, 

 stride, brown, slightly shining; teeth rather small, smooth: 

 muscle scars rather deep ; nacre bluish with blotches of pale 

 orange, iridescent. 



Length 75, height ^^^ diam. 19 mm. 



Srakeo River, Siam. 

 Pseudodon oralis Morlet. Jl. de Conch., XXXMI, 1889, p> 



197, pi. VII, fig. 3. — S[MPSox, Syn.. 1900, p. S>T^y. 



I have never seen this species, but it seems to be well dis- 

 tinguished from all the others by its short, elliptical, rhomboid 

 form, small teeth and blue nacre blotched with pale orange. 



Pseudodon thomsoni INIorlet. 



Shell irregularly long obovate. scarcely inflated, thin, in- 

 equilateral : beaks moderately inflated; dorsal outline slightly 

 and irregularly curved ; anterior end narrowed and rounded : 

 base line almost 'Straight throughout its anterior half, full and 



