NO. 1205. SY^'^OPSIS OF THE XATADES—SIMPSOX. 517 



Subgenus TETTNCILLA Rafinesque, 1819. 



Shell covered with broken rays, somewhat triangular, and without a 

 wide, radiate, posterior furrow. 



(Group of Truncilla triqtietra.) 



Shell greatly inflated, sharply truncate posteriorly; inflation of the 

 female shell at extreme post-basal point. 



1 t TRUNCILLA TRIQUETRA Rafinesque. 



- * Truncilla triqiieter Rafinesque, Ann. Gen. Sci. Phys. Brux., XIII, 1820, p. 300, pi. 



Lxxxi, figs. 1-4. — *Chenu, Bib. Couch., 1st ser., Ill, 1845, p. 15, pi. ii, tig. 



1. — ^Agassiz, Arch. fiir. Naturg., I, 1852, p. 44. 

 Unio triqueter Short and Eatox, Transylvania Jl., 1831, p. 79. — ^Say, Am. 



Couch., VI, 1834.—* Conrad, NewP. AV. Shells, 1834, p. 72.—* Ferussac, Guer. 



Mag., 1835, p. 27.—* Say, Ft. Ac. N. Sci. Phila., VI, 1853, p. 259.—* H. and A. 



Adams, Gen. Rec. Moll., II, 1857, p. 496.— * P^etel, Conch. Sam., Ill, 1890, 



p. 170. 



* Unio triangularis Barnes, Am. Jl. Sci., VI, 1823, p. 272, pi. xiii, fig. 17. — *Hil- 



DRETH, Am. Jl. Sci., X, 1828, p. 287, fig. — *Say, Am. Conch., No. 1, 1830, pi. 

 IV. — Short and Eaton, Transylvania JL, 1831, v. 78. — "Desha yes, An. sans 

 Vert., 2d ed., VI, 1835, p. 554 ; 3d ed., II, 1839, p. 674.—* Reeve, Couch. Syst., I, 

 1841, p. 118, pi. Lxxxix, fig. 9.— *Hanley, Test. Moll., 1842, p. 183 ; *Biv. Shells, 

 1843, p. 183. — * Catlow and Reeve, Conch. Nom., 1845, p. 64. — * Chenu, Bib. 

 Conch., Ist ser., Ill, 1845, p. 10, pi. i, figs. 4, 46; *Man., II, 1859, p. 137, fig. 

 662.— *S0WERBY, Conch. Icon., XVI, 1868, pi. lxvii, fig. 340.— * Calkins, Pr. 

 Ottawa Acad. Xat. Sci., 1874, p. 45. 



*Mya triangularis Eaton, Zool. Text Book, 1826, p. 221. 



^Margarita ( Unio) triangularis Lea, Syn., 1836, p. 18; 1838, p. 16. 



*Margaron (Unio) triangularis Lea, Syn., 1852, p. 23; 1870, p. 36. 



* Unio cuneatus Swainson, Phil. Mag., 1823, p. 112. 



* Unioformosus Lea, 'I'rans. Am. Phil. Soc, IV, 1834, p. Ill, pi. xvi, fig. 41 ; * Obs. I, 



1834, p. 121, pi. XVI, fig. 41.— *Chenu, 111. Couch., 18.58, pi. viii, figs. 12, 12ff, 

 126; *Man., 1859, II, p. 138, fig. 664. 



Ohio Eiver drainage; western ISTew York to southern Michigan; 

 Iowa; eastern Nebraska to Indian Territory. 



(Group of Truncilla hrevidefis.) 



Shell somewhat quadrate, not sharply truncate behind; post-basal 

 swelling of female in front of post-basal point and rounded below. 



t TRUNCILLA BREVIDENS Lea. 



Unio Irevidens Lea, Trans. Am. Phil. Soc, IV, 1834, p. 75, pi. iv, fig. 6; *Obs. I, 

 1834, p. 8.5, pi. VI, fig. 6.—* Hanley, Test. Moll., 1842, p. 198 ; * Biv. Shells, 1843, 

 p. 198, pi. XX, fig, 41. — *Catlow and Reeve, Conch. Nom., 1845, p. 56. — 

 *PI. and A. Adams, Gen. Rec. Moll., II, 1857, p. 492.— * Chenu. 111., Conch., 

 1858, pi. VIII, figs, 6, 6a, 66.— "P^tel, Conch. Sam,, III, 1890, p. 146. 



"Margarita (Unio) irevidens TuV^A, Sjn., 1836, -p. 29; 1838, p. 21. 



*Margaron ( Unio) hrevidens Lea, Syn., 1852, p. 32 ; 1870, p. 50. 



^A t placed before a species indicates that the type, or what are believed to be 

 authentic specimens have been examined by the writer. 

 ^Au * in front of a reference indicates that it has been verified. 



