NO. i2or,. svxoi'srs or THE XAIADESSIMI'SOX. 583 



Genus CRISTARIA Schumacher, 1817. 

 (Type, Dipaas plicatns Leach. > 



Barbala HUMPHREYS, Mus. Col., 1797. 

 Hipsas LEACH, Zool. Miscellany I, 1814, p. 119. 

 Criztaria SCHUMACHER, Essai Nouv. Syst., 1817, p. 107. 

 Appius (LKACH), Menke. Syn., 2d ed., 1828, ? p. 106. 

 ' SymphyHoia LEA (part), Tr. Am. Phil. Soc., 1830, p. 445. SWAINSON, Mai., 1840, 



p. 288. 



Dianisotis KAFINESQUK, Cont. Monog., 1831, p. 7. 

 Dipsax VOIGT, Cuvier, Thierreich, III, 1834, p. 493. 

 Barbata, SOWERBY, Conch. Man., 1842, p. 81. 

 Clione GISTEL, Nat. Sur. Hoh. Schule Bearb., 1848. 



Shell generally thin, elliptical, more or less winged posteriorly; beaks 

 rather low, sculptured with fine, somewhat doubly-looped ridges at 

 first, and later with coarse, low, concentric bars, which are nearly par- 

 allel with the growth lines; epidermis smooth, often somewhat rayed ; 

 hinge teeth imperfect; pseudocardiuals feeble or wanting when pres- 

 ent consisting of a single compressed tooth in each valve; laterals 

 single, remote, compressed, sometimes wanting in adult shells. 1 



Subgenus CRISTARIA. Schumacher, 1817. 

 (Type, Dipsas plicatns Leach.) 



Shell large, thicker in front, strongly alate posteriorly, with two or 

 more slightly developed radial ridges on the posterior slope and a row 

 of plications above them; hinge line regularly curved; dorsal scars 

 forming a row running obliquely downward and forward: anterior 

 scars often blurred, posterior faint. 



t CRISTARIA PLICATA Leach. 



* Dipsas plicatus LEACH, Zool. Miscellany, I, 1815, p. 120, pi. Lin. 2 * SOWERBY, 



Conch. Man., 1839, fig. 142. *CHENU, Bib. Conch,.lst ser., Ill, 1845, p. 15, pi. 



vi, fig. 1. * MORELET, Ser. Conch., IV, 1875, p. 332. *HEUDE, Conch. Fluv. 



Xank., 1879, pis. xxxin, xxxiv, LI, fig. 94. 



My til H s plicatus SOLANDER, in Gray, Ann. of Phil., IX, 1825, p. 27. 

 Appius plicatus GRAY, in Meuke, Syn. Meth. Moll., 1830, p. 106. 



* Margarita (Dipsas) plicatus LKA, Syn., 1836, p. 47; 1838, p. 28. 



* Margaron (Dipsas) plicatus LEA, Syn., 1852, p. 46; 1870, p. 74. 



* Unio plicatus SOWERBY, Conch. Icon., XVII, 1868, pi. LIV., fig. 280. 



* Dipsas plicata TROSCHEL, Arch, fur Naturg., XIII, 1874, p. 272. * KOBELT, Abh. 



Senck. Nat. Ges., XI, 1879, p. 429, pis. xv-xvn, xvm, fig. 1. 



* Barbala plicata H. and A. ADAMS, Gen. Rec. .Moll., II, 1857, p. 501, pi. cxvn, 



figs. 4, 4a. 



* Anodonta plicata SCHRENCK, Keis. and F. Am. Lande, II, 1867, p. 704, pi. 



xxvn, fig. 4. 



1 The animal has been described in Japanese, but the paper containing the descrip- 

 tion is inaccessible to me. 



2 This seems to be the first authentic description of this species. It has been 

 claimed that the Mytiliin dubiu* of Gmelin is this, bnt he refers to figures 733, pi. 82, 

 in the eighth volume of Chemuit/, which, I am quite certain, is not the species in 

 question. 



