﻿486 SVMI'JIVXOTA 



'i'lie name : iridis is credited to Rafinesque hv most authors, 

 but his description of that species is not sufficiently clear to 

 distinguish it from other memhers of the i^roup ; besides, this 

 form l;eloni;s exclusively in the Atlantic drainage and not in 

 the CJhio River Valley, Ratines(jue's locality. 1 cannot see any 

 specific difference between this and Lea's Unio hyalinus and 

 his perteniiis, which seem to me to be merely southern speci- 

 mens of this form. 



SvMi'UVNoTA Di<;coK.\^'A (Lca). 



Shell long rhomboid, scarcely subsolid, subcompressed, in- 

 equilateral ; beaks low, not inflated, their sculpture consisting 

 of doubly-looped, subnodulous ridges with a few radiating 

 threads behind ; posterior ridge low, double, ending behind just 

 at or above the base in a biangulation ; surface with delicate, 

 concentric striae ; epideniiis yellowish-green or greenish-yel- 

 low with wavy, green rays, subshining; left valve with an 

 irregular, arched tooth under the beak and a small one in 

 front, with two delicate laterals; right valve-with a compressed 

 pseudocardinal and one lateral; nacre bluish or i>inkish-white. 



Length Co, height ^^, diam. 18 mm. 



Length 74, height 42, diam. 23 mm. 



X'irginia to South Carolina. 



'J\vpe locality, Abbeville District, S. C. 

 Unio decoratiis Lka, Tr. Am. Phil. Soc, X. 1852, p. 257, pi. 



XIII, fig. 6; Obs.. V, 1852, p. 13, pi. XIII, tig. 6. — Sowerby, 



Conch. Icon.. X\'l, 1868, pi. xci, fig. 496. 

 Mari^^aron (Unio) dccoratus Lea, Syn.. 1852, p. 19; 1870. p. 29. 

 Symphynota decorata Simpson, Syn., 1900, p. 664. 

 Unio insolidus Lea, Pr. Ac. X. Sci. Phila.. II, 1872, p. 159; Jl. 



Ac. X. Sci. Phila.. VIII. 1874, p. 40. pi xiii. fig. t,7 \ Obs., 



XIIT, 1874. p. 44, pi. XIII, fig. 37- 



I believe that Lea's Unio decoratiis is the same as his U. 

 insolidus. The former is not quite so distinctly biangulate be- 

 hind as the latter, though a second specimen from the type 

 localitv is more biangulate than the type. T can see no essen- 



