﻿GLKIiULA 287 



sacs separated from each other by a sulcus as in Lampsilis: 

 palpi very large, wide, wrinkled ; mantle having a wide, slightly 

 thickened border, douible edged, the inner being beautifully 

 toothed ; branchial opening papillose ; anal crenulate ; foot 

 small. 



'i\pe, Unio rotmidata Lamarck. 



At the time of writing the Synopsis I felt a little doubtful 

 as to the systematic position of this peculiar and isolated form. 

 Recently Mr. Lorraine S. Frierson, who has been making a 

 careful study of the anatomy and shell characters of the Unio- 

 nidae of Louisiana has discovered that the beaks of perfect 

 specimens show no sculpture whatever. He has examined 

 gravid specimens and finds that the marsupium occupies the 

 hinder part of the outer gills, much as in Lampsilis. On pres- 

 sure the ovisacs were extruded from the gills, they were flat- 

 tened in cross section and were about one-half of an inch in 

 length. 



The shell of this form is quite different from that of any 

 other I know, seeming to combine some of the characters of 

 Lampsilis and some of those of Quadnila. Tt is short, rather 

 inflated, often solid, subtriangular or short elliptical and is 

 often more or less biangulated behind, the latter character 

 rarely being seen in the slightest degree in Lampsilis. The 

 pseudocardinals are curiously radically split. 



These radial lamellae are often sharply serrate and they re- 

 call the teeth of some of the South American species of Diplo- 

 don. 



It is probable that the apparent radial sculpture shown in 

 eroded specimens in due to a real radiating structure of the 

 shell. This character exists in many Naiades as well as in some 

 of the heavy species of Venus, but does not appear unless the 

 shell has begun to disintegrate. 



Gi.RHui.A ROTUNDATA (Lamarck). 



Shell somewhat elliptical, inflated, rather solid ; beaks gen- 

 erally flattened or compressed, though often full in old speci- 

 mens, without sculpture ; posterior ridge moderate, angular and 

 sometimes slightly double : epidermis brownish, cloth-like in 



