101 
VENUS turgida. 
TAB. CCLVI. 
=p 
Spec. Cuar. Orbicular, gibbose, with concentric 
ridges; valves thick, with tumid crenulated 
edges. 
=< 
Tue ridges upon this shell are variable according to 
the age or state of preservation: in some specimens they 
are sharp and prominent, in others they are scarcely ele- 
vated. The tumid edge does not appear until the shell 
has attained its full growth, when it is sufficiently re- 
markable. The lunette is defined by a line ; it is cordi- 
form. The hinge possesses the small tooth that marks 
the genus Cytherea of La Marck. 
I have this among the numerous contributions from 
the crag of Norfolk and Suffolk, lately made to me by 
the Rev. G. R. Leathes. The specimen of which two 
views are given at fig. 1. is in excellent preservation, 
and shews the prominent ridges, the other specimen ap- 
pears to have been worn: the first is from Ramsholt, 
near Woodbridge, out of a newly discovered bed of 
clay; the latter from Woodbridge. I have alsoa younger 
white shell with a thin edge from Roydon. 
