﻿TRUNCILIvA 27 



The shells in the Lea collection are the only ones T have 

 seen of this form, which are typical, though they show consid- 

 erable variation and some of them approach the type. 



Truncilla sampsonii (Lea). 



Shell solid, inflated, subquadrate or trapezoid, inequilateral 

 with high full beaks, whose sculpture is feeble and corrugated ; 

 lunule wide but small ; posterior ridge low, narrowly rounded, 

 placed near the dorsal line ; median ridge rounded, rarely 

 showing vestiges of knobs ; surface rather smooth, usually with 

 a concentric constriction at the rest marks ; epidermis straw- 

 color or yellowish-green with numerous green rays, silky ; teeth 

 solid ; pseudocardinals triangular, laterals double in each 

 valve. Male shell not difl:'ering greatly in outline from that 

 of the female. Female shell with the marsupial swelling but 

 slightly produced, differing little in color or texture from the 

 rest of the shell, sometimes having radial grooves. The nacre 

 of male and female shells varies from bluish-white to salmon. 



Length (male) 43, height 33, diam. 24 mm. 



Length (female) 45, height 35, diam. 29 mm. 



Wabash River ; Tennessee ? 



Type locality, Wabash River, New Harmony, Ind. 

 Unio sampsonii Lea, Pr. Ac. N. Sci. Phila., VL 1861, p. 392; 



Jl. Ac. N. Sci. Phila., V, 1862, p. 192, pi. xxv, fig. 261 ; Obs., 



IX, 1863, p. 14, pi. xxv, fig. 261. 

 Margaron (Unio) sampsonii Lea, Syn., 1870, p. 40. 

 Truncilla sampsonii Simpson, Syn., 1900, p. 523. 



This seems to be a smaller species than T. perplexa, is gen- 

 erally more inflated, is almost entirely without anything like 

 knobs and the shells of both male and female are subquadrate 

 or trapezoid. The species does not seem to be common and 

 It is possible that none of the specimens I have seen are fully 

 adult. 



Truncilla propinqua (Lea). 



Shell subtriangular to subelliptical, inflated, solid, very in- 

 equilateral ; beaks full and high ; lunule wide ; posterior ridge 

 rather narrowly triangular ; median ridge full ; sometimes it 



