﻿LAMPSILIS 77 



often marked by a sulcus, tawny to pale, dirty olive, sometimes 

 feebly rayed ; ligament large and full ; left valve with two tri- 

 angular pseudocardinals and two strong laterals; right valve 

 with two pseudocardinals. the hinder triangular and large, 

 the anterior small, there is sometimes a third small pseudo- 

 cardinal behind the other two, there is one strong high lateral ; 

 posterior muscle scars large, rather deep; anterior scars very 

 deep and rough ; beak cavities deep ; nacre white or salmon- 

 tinted. The male is pointed behind about midway up from the 

 base ; the female shell has a well-developed post-basal swelling. 



Length (male) 85, height 70. diam. 34 mm. 



Length (female) 75, height 63, diam. 35 mm. 



Ohio and Cumberland Rivers ; west to the Mississippi River, 



Type locality, Muskingum River, Ohio. 

 Unio orbicnlatus Hii.drijth, Am. Jl. Sci., XIV, 1828, p. 284.— 



Hanley, Biv. Shells, 1843, P- 192, pl- xxi, fig. 2.— Kuster, 



Conch. Cab., 1861, p. 216, pl. lxxi, figs. 3, 4.— Sowerby, 



Conch. Icon., XVI, 1866, pl. xijv, fig. 239. 

 Margarita (Unio) orbicnlatus Lea, Syn., 1836, p. 25 ; 1838, 



p. 19. 

 Margaron (Unio) orbicnlatus Lea, Syn., 1852, p. 28; 1870, 



P- 43- 

 Lampsilis orbicnlatus Simpson, Syn., 1900, p. 540. 

 Lampsilis orbiculata Ortmann, Ann. Car. Mus., VIII, 1912, 



p. 353- 

 Unio abruptus Say, Am. Conch., No. II, 183 1, pl. xvii,— 



Chenu, Bib. Conch., ist ser., Ill, 1845, p. 24, pl. vi, figs, i, 



icr, lb. 

 Unio cyclips Ferussac, Guer. Mag., 1835, p. 28. 

 Unio crassus Conrad, Monog., IV, 1836, p. 34, pl. xvi. 



Lighter colored, less inflated, and more humped than L. hig- 

 ginsii, the latter having much the fonn of Obovaria ellipsis 

 Ivca. It is lighter colored and more humiped, it has a stronger 

 posterior ridge and is less convex than the form I have called 

 higginsii var. grandis. The young shell of orbicnlata is more 

 elongated and the beaks are less elevated than is the case in L. 



