﻿322 TRIToGONIA 



Unio lunuhitiis I'katt. I'r. Dav. Acad. N. Sci., I, 1876, j). 



p. 167, pi. XXXI, fig:. 1. 

 Ouadnila lacliryniosa var. hinulata SiMi'Sox, Syn., 1900, p. 



777- 



Conrad's description of Unio nobilis is not very explicit and 



he figures two specimens. His fignre No. 2 is the same as 

 Say's apiculatiis. 1 am sure. Fignre 3 represents a large shell 

 114 millimeters in length, considerahly drawn out and rounded 

 behind at the termination of the douhle posterior ridge. I had 

 never seen anything like it at the time I wrote the Synoi)sis 

 and thought it might be an abnormal s])ecimen. Recently 

 Mr. Lorraine S. Frierson has sent me two shells, one of 

 which, from Grand River. Missouri, is almost exactly like 

 Conrad's figure 3, being drawn out behind and decidedly 

 wedge-shaped when view^ed from above. The other is a much 

 shorter shell, more inflated in proportion to its length and is 

 almost squarely truncated behind, in fact the upper part of the 

 truncation overhangs a little. Some specimens are tubercu- 

 late throughout ; others show little more than the two rows 

 of strong knobs, and a valve from the Red River of the North 

 is slightly compressed and almost destitute of nodules. I am 

 inclined to believe that Pratt's Unio liinulotiis from near Rock 

 Island, Illinois, is a smooth inflated form of Conrad's nobilis, 

 a male shell probabl}-. 



I cannot be sure as to the relationships of this species, but 

 am inclined to jjlace it with Trito(:;onia. The female of Lea's 

 Unio lachrymosiis has all four of the gills filled with embryos 

 forming smooth pads, and the shells, so far as I have seen, 

 are not dimorphic. I have never seen a gravid Unio tiihcrcu- 

 latus of Barnes, but specimens recently examined in which 

 the shell was drawn out into a rounded wing behind appeared 

 to have the outer gills recently filled, as the apparent ovisacs 

 were still distended and seemed to be separated by sulci. The 

 inner gills gave no indication of having been filled with young. 



Tritogonia conjugans (B. H. Wright). 



• Shell long rhomboid, solid, inflated, inequilateral ; beak? 

 probably low and compressed : posterior ridge high, and in 



