201 
TEREBRATULA biplicata. 
TAB. XC. 
Spec. Char. Oblong, gibbous; beak prominent; 
sides rounded ; front straightish, when full 
grown, elevated with two distant large plaits. 
Fig. 1. 
j3. sides rather angular^ straightish towards 
the fronts smaller and broader than a. Figs. % ' 
3j 4, and 5. 
Of the two varieties of this shell, the larger one is longer 
in proportion to its width, and more gibbous: the younger 
shells of either seem scarcely to be plaited, and are rather flat. 
I was favored with some of the shells, &c. found in dig- 
ging in the Castle Hill, Cambridge, by Dr. Clarke and 
H. Warburton, Esq. about ten years since; among the 
parcel from the latter gentleman was the middle specimen 
here figured ; it was among the marly goult with the green 
and irony sand, &c. see Brit. Min. tab. 184. Its resem- 
blance to those surrounding it made me place it here, as 
I think they ought to be identified. It is, however, larger, 
and the shell not much more altered than reeent shells 
sometimes are. I possess the same variety from Limerick, 
but more mutilated, the shell not more changed, but having 
become a shelter for small worms: also another specimen 
not infected with worms : they appear to be of the same 
age and size. * Hunstanton Cliff in Norfolk affords the 
