143 
PETRICOLA laminosa, 
TAB. DLXXIII. 
Spec. Char. Ovate,, gibbose, ornamented with erect 
concentric laminae ; posterior side subcunei- 
form ; one broad bifid tooth in the left valve^ 
two small teeth in the other. 
This is the largest species of Petricola known ; the la- 
minae upon its surface are entire, rather thick, and tole- 
rably close set ; they distinguish it from every other. 
Found by the Rev. G. R. Leathes in the Suffolk Crag; 
who has kindly allowed us the use of the only specimens 
he has. 
Fig. 1. represents two views of the left valve of a re- 
gularly grown shell : Fig. 2. the same valve from a dis- 
torted individual : Fig. 3 . the inside of the right valve, 
also a distorted shell. 
