124 
I figure these on a presumption that they may lead to 
information, should any one find them and determine that 
they belong to the Genus Unio or otherwise ; as far as I 
yet know, specimens exposing the inner construction 
haye not been found. 
UNIO hybrida. 
TAB. CLIV.---Fig 2. 
Spec. Cuar. Oblong, ovate, anterior side sub- 
acuminate ; surface imbricated; beaks re- 
curved, acute ; shell thick. 
—— 
Tus differs from the recent Unio oyatus principally in 
the largely imbricated surface and thickness of the shel] 
with the acute beaks; breadth about twice the length. 
The specimen figured is from Nottinghamshire, 
