NO. 1205. SYNOPSIS OF THE NAIADES SIMPSON. 579 



Beak cavities shallow; dorsal scars numerous, extending from the cav- 

 ity downward and forward. Anterior muscle scars three, distinct, pos- 

 terior large, indistinct; front end of the shell usually thickened; a row 

 of plications often occurring just below the laterals, as in Cristaria. 

 Animal unknown. 



(Group of Hyriopsis butlatus.) 



Shell somewhat trapezoidal, with a posterior ridge, biangulate behind, 

 with a very high, pointed, triangular, posterior wing, and a smaller, 

 pointed one in front, which projects forward; beaks low, sculpture not 

 seen; epidermis brown; pseudocardinals broken up into denticles: 

 hinge line slightly curved; the three anterior muscle scars separate and 

 deep; dorsal scars not extending greatly downward in front; nacre 

 bluish white. 



tHYRIOPSIS BIALATUS Simpson. 1 



* I'nio delphiniis GRUNER Arch, fiir Xaturg, 1, 1841, p. 276, pi. ix, tigs. 1, la-c. 



* DKLESSERT, Rec. Coq. Lam., 1841, pi. xix. fig. 3, 3, 36. *LEA, Tr. Am. Phil. 

 Soc., VIII, 1843, p. 218, pi. xvn, fig. 35; *Obs., Ill, 1842, p. 56, pi. xvn, 

 fig. 35.- ' KUSTER, Conch. Cab. Unio, 1852, p. 18, pi. n, figs. 2-4. *HAXLKY, 

 Biv. Shells, 1856, p. 381, pi. xx, lig. 44.- H. and A. ADAMS, Gen. Rec. Moll., II, 

 1857, p. 498. *CHENU, Man., 1859, II, p. 143, tig. 707. SOWERBY, Conch. Icon., 

 XVI, 1866, pi. XLIII, fig. 238. *MORELET, Series Conch., IV, 1875, p. 345. 



* P.ETEL, Couch. Sam., Ill, 1890, p. 150. 



* Margaron ( Unio) delphlnus LEA, Syn. 1852, p. 19; 1870, p. 28. 



* Unio megapterus MORELET, J. tie Conch., XII, 1863, p. 159. * P^ETEL, Conch. 



Sam., Ill, 1890, p. 158. 



Southeastern Asia, including Cambodia, Siam, and the Malay Penin- 

 sula. 



(Group of Hyriopsis cumingii.) 



Shell rather thin, with a high wing posteriorly, and a smaller one in 

 front; beaks greatly compressed, their sculpture at first consisting of 

 fine and later of coarse concentric ridges, extending well on to the 

 disk; corrugations on the posterior slope distinct. 



HYRIOPSIS CUMINGII Lea. 



* I 'nio cumingii LEA, Pr. Ac., N. Sci. Phila., VII, 1852, p. 54. * LEA, Jl. Ac. 



N. Sci. Phila., IV, 1860, p. 240, pi. xxxv, fig. 120; * Obs., VII, 1860, p. 58, pi. 

 xxxv, fig. 120. *H. and A. ADAMS, Gen. Rec. Moll.. II, 1857, p. 498. 



* SOWERBY, Conch. Icon., XVI, 1866, pi. XLIX, fig. 264. *HEUDK, Conch. 

 Fluv. Nank., VIII, pi. LXIV. 



*Margaron ( Unio) cumingii LEA, Syn., 1852, p. 19 ; 1870, p. 28. 



China. 



'I regret that Gruner's well-known name delpJiimis was previously used for a Unio 

 by Spengler, and the term megapterus of Morelet was applied by Rafinesque to a 

 Metaptera ( Unio) and used by Chenu under the generic name Unio before 163. It 

 will therefore have to have a new name. 



-Lea described this species under the, above name, not knowing that it had been 

 already applied to the same species by Grnner. 



