PLATE 27. 
NGS Lip Ops) COAST G56 Goch doko aeoe he sa55 Hooeno cedouodocdasGo06se goscco cone 
a. Left valve; natural size. 
Fig. 2. UNIO DANA? 
a. Exterior view ; right valve; natural size. 
b. Interior view of a left valve. 
Both examples are from Black Buttes Station, Wyo. 
Fic. 3. CASSIOPELLA TURRICULA 
a, b,c,and d. Lateral views of different examples; natural size. 
eand f. Two examples, showing the aperture and small umbilicus. 
g. Basal view of anotherexample, showing the umbilicus, the diameter 
of which is proportionately a little larger than the average. 
