NO. 1205. SYNOPSIS OF THE JNAFADES— SIMPSON. 885 



tDIPLODON PATAGONICUS d'Orbigny. 



* Unio patagonica d'Orbigny, Guer. Mag., 1835, p. 37; *Voy. Am. Mer., 1843, p. 



610, pi. Lxx, tigs. 1-4, 



* Margarita ( Unio) patagonicus Lea, Syn., 1838, p. 25. 



* Unio patagonlcm Hanley, Test. Moll., 1842, p, 208; * Biv. Shells, 1843, p. 208, 



pi. XXII, fig. 16. — * Catlow and Reeve, Conch. Norn., 1845, p. 62. — * H. and 

 A. Adams, Gen. Rec. Moll., II, 1857, p.461.— * Reeve, Conch, Icon., XVI, 1865, 

 pi. XXI, fig. 93.—* Strobel, Mat. Mai., Pt. 1, 1874, p. 72.—* P.etel, Conch, 

 Sam., Ill, 1890, p, 162. 



* Mar gar on ( Unio) patagonicus Lea, Syn., 1852, p. 38; 1870, p, 61. 



Patagonia. 



tDIPLODON ACUTIROSTRIS Lea. 



* Unio acuiirostris Lea, Pr. Ac. N. Sci, Phila,, X, 1866, p. 34; *J1. Ac. N, Sci. 



Phila., VI, 1868, p, 270, pi. xxxv, fig, 84; " Obs., XIII, 1869, p, 30, pi. xxxv, 

 fig. 84. 



* Mar gar on ( Unio) acuiirostris Lea, Syn., 1870, p. 58, 



South America. 



(Grroiip of Diplodon qnadrans.) 



Shell subtrapezoicl, slightly truncate iu front, nearly equilateral, 

 greatly inflated, its greatest diameter below the beaks, from which it 

 is wedge-shaped in front and behind, solid, with a decidedly rounded 

 posterior ridge; epidermis brownish, concentrically striate, beaks full 

 but not high, ligament long and slender; pseudocardinals large, com- 

 pressed, striate and crenulate, double in the right valve, single in the 

 left; laterals curved, crenulate; beak cavities rounded; anterior cica- 

 trices deep, confluent; nacre white. 



Animal unknown. 



DIPLODON QUADRANS Lea.i 



*Unio quadrans Lea, Pr, Ac. N. Sci, Phila., IV, 1859, p. 306; *J1, Ac, N, Sci, 

 Phila,, IV, 1860, p. 360, pi. lxi, fig, 185; * Obs., VIII, 1860, p. 42, pi, lxi, fig. 

 185.—* B, H, Wright, Check List, 1888, 



* Margaron ( Unio) quadrans Lea, Syn,, 1870, p. 36, 



South America ( ■?). 



Subgenus CYCLOMYA Simpson, 1900. 

 (Type, Unio fnnebr alls Lea.) 



Shell obovate to suborbicular, narrowed in front, produced just behind 

 the center of the base, generally slightly pointed about the middle of 

 the posterior end, with a scarcely jjerceptible posterior ridge and a 

 slight dorsal wing behind; beaks high, irregularly radial; hinge line 



' Only one specimen of this shell is reported, this being iu the Wheatley collection, 

 and credited to Texas, The beak sculpture is all eroded away, but I am almost sure 

 it is a South American shell, allied, jjerhaps, to D. apprimns, uruguayensis, and possi- 

 bly to Hupe's Unio orhignyi. 



