PARRKYSIA 1103 



Pscudodon ponderosa Preston, Pr. Mai. Soc. London, VIII, 

 1909, p. 202, pi. VIII, fig-. I. 



The following are unfigured or indeterminate species. 

 Spatha compressa von Martens, Proc. Zool. Soc. Lond.. i860, 



p. 66. Siam. 

 Pseudodon sidcatum Rochebrune, Bull. Soc. Phil., 7th ser., 



VI, 1882, p. 41. Mekong River, Cochin China. 

 Pseudodon pierrci Rochebrune, Bull. Soc. Phil, VI, 1882, p. 



41. Cochin China. 

 Pseudodon mabilli Rochebrune, Bull. Soc. Phil., VI, 1882, 



p. 41. Cochin China, Cambodia. 

 Pseudodon anodontmurn Rochebrune, Bull. Soc. Phil., VI, 



1882, p. 41, Cambodia. 



Genus PARRKYSIA Conrad, 1853. 



Parrcysia Conrad, Pr. Ac. N. Sci. Phila., VI, 1853, p. 267. — 



Ortmann, Ann. Car. Mus., VIII, 1912, p. 276. 



Shell solid, inflated, oval to subrhomboid, with full, high, 

 zigzag, radially sculptured beaks, the sculpture often extend- 

 ing over the disk ; epidermis smooth and bright, sometimes a 

 little rayed ; with two irregular pseudocardinals in the left 

 valve which are more or less broken into ragged denticles, or 

 are strongly, vertically striate, and two laterals, the lower the 

 larger ; right valve with one, sometimes two pseudocardinals, 

 the upper small, compressed, and a few tubercles behind them, 

 with two laterals, the upper the larger ; cavity of the beaks 

 rather deep, not compressed ; dorsal scars under the hinge, not 

 visible; the two upper anterior muscle scars very deep, con- 

 fluent, the lower linear; nacre white to salmon, iridescent be- 

 hind. 



Length 65, height 27.5. diam. 15.5 mm. 



Type, Uiiio mulfidentatus Philippi. 



In the above reference Conrad gives the name Parrcysia and 

 refers to Unio midtidcntatns Parreyss, which may be taken 

 as the type. I do not know that he ever described the group. 



The species, which I have placed in the above named assem- 

 blage, seem, so far as conchological characters show, to be 



