834 PROCEEDINGS OF THE NATIONAL MTSETM. VOL.XXII. 



DALLIELLA SERRADELLI Drouet. 



* I'tiio serradelli DROUKT, Jl. de Conch., XL, 1892, p. 86. 



Philippines. 



(Group of Dalliella insularis.) 



Shell subsolid, subrhomboidal biaugulate behind, pseudocardinals 

 and laterals blurred, not greatly compressed; nacre lurid, tinged 

 purplish. 



t DALLIELLA INSULARIS Drouet. 



*Pseudodon insularis DROUET, Rev. Biol. Fr., VI, 1894, p. 217, fig. 2. 

 Borneo; Palawan Island, Philippines. 



t DALLIELLA CRASSA Drouet. 



*Pseudodon crassus DROUET, Jl. de Conch., XL, 1892, p. 93. *DROUET and CHAPEH, 

 Me"m. Soc. Zool. de Fr., V, 1892, p. 151, pi. vi, figs. 1-3. 



Borneo. 



The following is an unflgured species. 



* Unio semmelinki vox MAKTENS, Sitzber. Ges. Nat. Fr. Ber., 1891, p. 111. 

 Southeast Borneo. Possibly a Dalliella. 



Genus PSEUDODON Gould, 1844. 

 (Type, Anodon salwiniana Gould.) 



Paeudodon GOULD, Pr. Boat. Soc. Nat. His., 1844, p. 161. 

 Monodontina CONRAD, Pr. Ac. N. Sci. Phila., 1853, p. 269. 

 Triyonodon CONRAD, Am. Jl. Couch., 1, 1865, p. 233. 

 Monocondylus MORELET, Rev. et Mag., 1866, p. 167. 

 Pseudodus DE MORGAN, Bull. Soc. Zool. Fr.,X, 1885, p. 422. 



Shell oval to elongate, having two posterior ridges and often one or 

 two slight, radiating elevations above on the posterior slope, above 

 which there is usually a small wing; beaks rather low, sculpture 

 unknown ; ' epidermis dark, often having a few faint wrinkles on the 

 posterior slope, without rays when adult. There is a single, smooth 

 tooth in each valve, with occasional vestiges of a second; laterals 

 nearly or quite wanting; beak cavities shallow: dorsal scars conspicu- 

 ous, deep, distinct, 4 to 7 in a row under the hinge; anterior scars irreg- 

 ular; nacre generally dull and lurid. 



Animal 2 having the branchiae wide and rounded behind, becoming 



'One or two authors in describing species say that the beaks are entirely smooth. 

 It is probable that in most oases they have zigzag radial sculpture. Although I 

 have examined a large number of shells belonging to the group, many of which were 

 young, they were all so badly eroded that the beak sculpture was entirely destroyed. 



2 Deshayes and Julien figure but do not describe the animal of P. moreleti in Nouv. 

 Arch, de Mus., X, pi. v. I am only able to make out part of the characters from this 

 really excellent figure. 



