﻿6 TRUNCILI.A 



Length (male) O9, height 48.5, diam. 35 mm. 



Length (male) 55, height 36, diam. 31 mm. 



Length (female) 52, height 34, diam. 39 mm. 



Length (female) 45, height 28, diam. 30 mm. 



(Jhio River drainage ; western New York to southern Mich- 

 igan ; Iowa ; eastern Nebraska to Indian Territory. 



T^'pe locality, Falls of the Ohio. 

 Truncilla triqneter RaFinesour, Ann. Gen. Sci. Phys. Brux., 



Xin, 1820, p. 300, pi. Lxxxi, figs. 1-4. — Chenu, Bib. Conch., 



I at sen, IH, 1845, P- 15. P^- ". %• i- 

 Unio triqneter Short and Eaton, Transylvania Jl., 183 1, p. 



79- 

 Truncilla triquetra Simpson, Syn., 1900, p. 517. 

 Unio triangularis Barnes, Am. Jl. Sci., VI, 1823, p. 272, pi. 



XIII, fig. 17. — HiLDRETH, Am. Jl. Sci., X, 1828, p. 287, fig. 



— Say, x\m. Conch., No. i, 1830, pi. iv. — Reeve, Conch. 



Syst., I, 1841, p. 118, pi. Lxxxix, fig. 9. — Chenu, Bib. 



Conch., ist ser.. Ill, 1845, p. 10, pi. i, figs. 4, ^b; Man., II, 



1859, p. 137, fig. 662. — SowKRBY, Conch. Icon., XVI, 1868, 



pi. i.xvii, fig. 340. 

 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 cuneatu^ Swainson, Phil. Mag., 1823, p. 112. 

 Unio formosus Lea, Trans. Am. Phil. Soc, IV, 1834, p. iii, 



pi. XVI, fig. 41 ; Obs. I, 1834, p. 121, pi. XVI, fig. 41. — Chenu, 



111. Conch., 1858, pi. VIII, figs. 12, 120, 12b; Man., 1859, II. 



p. 138, fig. 664. 



It will be observed from the above measurements that the 

 female shell is much smaller than that of the male and that it 

 is more inflated in proportion to height. It is more strongly 

 and sharply truncate posteriorly, and is less high in propor- 

 tion to length than that of the male. The marsupial swelling 

 is but slightly developed, but it shows radial sculpture to its 

 front edge. The beak sculpture of this species is very faint, 



