﻿TRITOGONIA 319 



heavy shells may be partly double; beak cavities moderately 

 deep, compressed ; anterior scars rough ; posterior scars oval ; 

 nacre white, rarely purple. In this remarkable species the 

 male shell is obliquely truncate at the posterior base, behind the 

 posterior ridge and ends in a somewhat blunt point consider- 

 ably above the base line. From this point running towards 

 the beaks there is generally a row of low, broad nodules or 

 knobs that extend upward in ridges. In the female shell this 

 area is much smoother, and is extended into a broad, rounded 

 wing. 



Length (male) 125, height 80, diam. 40 mm. 



Length (male) 150, height 88, diam. 50 mm. 



Length ( female) 125, height 70, diam. 35 mm. 



Length (female) igo, height 103, diam, 48 mm. 



Mississippi drainage ge«ierally ; streams falling into the 

 Gulf of Mexico from the Alabama system west to central 

 Texas. 



Type locality, Wisconsin. 

 Unio tiiberculatns Rajjnks, Am. Jl. Sci., VI, 1823, p. 125, pi. 



VII, figs. 8a, Sb. — Reeve, Conch. Syst., I, 1841, p. 118, pi. 



Lxxxviii, fig. 5. — Hanley, Biv. Shells, 1843, P- 182, pi. xx, 



fig. 27. — PoTiEZ and Michaud, Gall. Moll., 1844, p. 158, pL 



I.X, fig. I. — Reeve, Elements of Conch., i860, II, pi. xxxni, 



%■ T83. 

 Margarita (Unio) tnberculatus Lea, Syn., 1836, p. 17; 1838, 



p. 16. 

 Margaron (Unio) tuhercnlatiis Lea, 1852, p. 23 ; 1870, p. 34. 

 Mya tubcrculata Eaton, Zool. Text-Book, 1826, p. 217. 

 Tritogonia tubcrculata Simpson, Syn., 1900, p. 608. 

 Ouadrnla tubcrculata Ortmann, Ann. Car. Mus., VIII, igi2, 



P- 254. 

 Unio pustulata Swainson, Treat, on Mai., 1840, p. 271. fig. 



Unio gigas Sowerby, Conch. Icon., XVI, 1867, pi. lvi, fig. 287. 

 Unio verrucostis Say, Am. Conch., VI, 1834. — Kuster, Conch. 



Cab., 1862, p. 273, pi. xcii, fig. I. — Sowerby, Conch. Icon., 



XVI, 1868, pi. I, fig. 4. 



