EXPLANATION OF PLATE XV, 
Figure 1. Unio aipposus Barnes. <j Juvenile. 
‘* 2. Unio cipsosus Barnes. 
‘* 3. Unio Gipposus Barnes. 2 
‘* 4, Unio Gipsosus Barnes. 
5. QUADRULA TRIGONA Lea. 
34 natural diameter. 
