)82 FROCEEDINGS OF THE NATIONAL MUSEUM. 



Genus CHAMBERLAINIA Simpson, 1900. 



(Type, Unio hainesianus Lea.j 



Shell large, very solid in front, thinner behind, round or round obo- 

 vate, without posterior ridge, alate on the post dorsal part when young ; 

 beaks full, sculpture not seen; surface without sculpture excepting a 

 few slightly pustulous corrugations on the posterior slope; epidermis 

 dull, not rayed; hinge curved; pseudocardiuals rather small, stumpy, 

 two in the left valve and one in the right; laterals short, remote, the 

 intervening hinge plate rounded, one lateral in the right valve and two 

 in the left, the upper the smaller, and all curved upward along their 

 inner edges; beak cavities not deep; dorsal muscle scars numerous, 

 deep, extending from the cavity downward and forward; area outside 

 the palleal line very wide; nacre lurid bronzy. Animal unknown. 



t CHAMBERLAINIA HAINESIANA Leai. 



^Unio liainesUmus Lka, Pr. Ac. N. Sci. Phila., VIII, 1856, p. 92; * Jl. Ac. N. Sci. 



Phil., Ill, 1857, p. 289, pi. xxi, fig. i ; «Obs. VI, 1857, p. 9, pi. xxi, fig. 1.— 



^'VON Martens, Pr. Zool. Soc. LoncL, 1860, Pt. 1, p. 15— * Sowerby, Couch. 



Icon., XVI, 1866, pi. xlvii, fig. 254."— " Mohelet, Ser. Couch., IV, 1875, p. 



312.— " P.ETEL, Conch. Sam., Ill, 1890, p. 154. 

 ^ Mar gar on ( Unio) Itainesianus Lea, Syn., 1870, p. 28. 

 * Unio imjyerialis Morelet, Eev. et Mag. Zool., XIV, 1862, p. 480. 



Siam. 



CHAMBERLAINIA PAVIEI Morelet. 

 " Unio paviei Morelet, J. de Conch., XXXIX, 1891, p. 241, pi. vii, tig. 3.'' 



Siam. 



t CHAMBERLAINIA DUCLERCI Rochebrune.^ 



"Unio duclerci Eochebrune, Bull. Soc. Phil., VII, 1882, p. 27, pi. i, fig. 2 (in 

 extract). 



Mekong; Eiver, Siam. 



1 The type consists of a single valve of a young individual. U. imperialis according 

 to its author attains a size of 142 mm. in height, 192 mm. in length, and 77 mm. in 

 diameter. I have seen a very fine specimeu in the Frederick Stearns collection 6 

 inches high and 8 iu length. It is one of the most magnificent Naiades in the world. 



-Credited bj' Sowerby to the Little Arkausas River. 



■'Very close to C. honsei, but more rounded, and having a higher wing. I do not 

 thiuk this can be the same as Morelet's Unio pairavus, described iu Latin in the 

 Journal in 1865, p. 227, and unidentifiable. 



^It is quite probable that this should form the type of a separate group, but the 

 only specimens I have seen, two badly eroded valves, hardly justifj' me in separat- 

 ing it. 



