PLICA TULA inflata. 
TAB. CCCCI X.—Jig. 2. 
Spec. Char. Suborbicular, gibbose, rather 
smooth, furnished with a few ridges and de- 
pressed spines ; both valves convex. 
Syn. Plica tula spinosa, Mantell GeoL Sussex 
j 9. 129 , i. 26,/ 13, 16 and 17. 
J'his is probably the largest species of Plicatula known : 
the smooth surface., and the small number of the ridges, 
composed chiefly of depressed spines, suffice to dis- 
tinguish it from the last, and the convexity of both valves 
will distinguish it from most Oysters. 
Small specimens of this have been taken for Plicatula 
spinosa by Mr. Mantell, but it is a very distinct 
shell ; it is found only in the lower beds of Chalk with- 
out flint, and that called sometimes Chalk Marl, but 
not in the Clay beneath. 
The specimens figured, were kindly lent me by Pro* 
fessor Sedgwick ; they are from the vicinity of Cam- 
bridge : I have others from Hamsey, by favour of BJr. 
Mantell. 
