124 
1 figure these ou a presumption that they may lead to 
information, should anyone find them and determine that 
they belong to the Genus Unio or otherwise ; as far as I 
yet know, specimens exposing the inner construction 
have not been found. 
UNIO hybrids 
TAB. CLXV .—Fig 2, 
Spec. Char. Oblong, ovate, anterior side sub- 
acuminate ; surface imbricated ; beaks re- 
curved, acute ; shell thick. 
This differs from the recent Unio ovatus principally in 
the largely imbricated surface and thickness of the shell 
with the acute beaks; breadth about twice the length. 
The specimen figured is from Nottinghamshire. 
