﻿SVMPHYNOTA 49 1 



an line ; base rounded, full behind the middle ; surface with 

 rude growth lines, often somewhat plicate on the posterior 

 slope ; epidermis dark green in young shells, blackened in old 

 ones, scarcely shining ; left valve with two strong, uneven 

 pseudocardinals, the hinder generally divided, sometimes some- 

 what A-shaped ; right valve with one or two pseudocardinals, 

 which are frequently split up and imperfect ; laterals very much 

 blurred in both valves ; muscle scars large ; nacre white, thick- 

 ened in front, with a wide border outside the jjallial line. 



Length 197, height 126, diam. 52. mm. 



Length 126, height 52, diam. t,^ mm. 



Upper Mississippi drainage, as far south as Arkansas on 

 the west ; Ohio River system ; upper St. Lawrence and its tri- 

 butaries ; north into the Mackenzie River. 



Type locality, Wisconsin ; Fox River. 

 Alasmodonta complanata Barnes, Am. Jl. Sci., VL 1823, p. 



278, pi. XIII, fig. 21. — Baker, Moll. Chicago, Ft. i, 1898, p. 



60, pi. VIII, figs. I, 2; IX, figs. 1-4. 

 Mya complanata Eaton, Zool, Text-Book, 1826, p. 222. 

 Symphynota complanata Lea, Tr. Am. Phil. Soc, III, 1830, p. 



448; Obs., L 1834, p. 62. — Simpson, Syn., 1900, p. 665. 

 Margarita {Margaritana) complanata Lea, Syn., 1836, p. 43; 



1838, p. 26. 

 Unio complanata Hanley, Biv. Shells, 1843, P- -^O- P^- ^^^' 



fig. 9. 

 Complanaria complanata Conrad, Pr. Ac. X Sci. Phila., VL 



1853, p. 261. 

 Baphia complanata H. and A. Adams, Gen. Rec. Moll.. 11, 



^'^S7^ P- .Soo. 

 Margaritana complanata Calkins. Pr. Ot. Acad., 1874, p. 46. 

 Alasmodon complanatus Soweri'.y. Conch. Man., 1842. p. 61. 



fig. 140. — KuSTER, Conch. Cab. L'nio, 1861, p. 199, pi. Lxv, 

 •fig. I. — SovvERBY, Conch. Icon., XV I, 1866, pi. l. fig. 266. 

 Complanaria gigas Sowerby, Conch. Man., 1839. fig. 141 ; 



1842, p. 115, fig. 141- 

 ? Megadowus gigas Swatnson. Tr. on Mai.. 1840. pp. 265. 



37^- 



