217 
TEREBRATULA digona. 
TAB. XCVI. 
Spec. Cuar. ‘Triangular, oblong, gibbous; beak 
prominent; sides rounded; front either convex 
or concave; when oid, bounded by two pro- 
minent anges alike in each valve. 
a ee 
Tus shell is very variable in its form, being sometimes 
almost globose, at others acutely triangular and rather 
depressed, the two angles of the front are continued a little 
way along each valve, and look as if they were produced 
by pinching the edges between the fingers ; the front between 
the angles is in some shells concave, in others straight or of 
different degrees of convexity. The surface when mag- 
nified is found to be minutely punctured. 
This is very common in the neighborhood of Bath; it is 
mentioned by Woodward, Walcot, &c. but we cannot be 
certain of synoayms at present, as there are so many varieties, 
and it may hereafter be found that in some soils they are 
more constantly of one particular form and color than of 
another. Walcot’s fig. 26 seems related to it, and he quotes 
W oodward, vol. 1, part 2, page 46, fig. 215, 216, and says 
specimens are ‘‘scarce; Woodward found them at Toghill, 
and he met with one or two nearer Bath.”’ I have expressed, 
figs. 1, 2, and 3, three varieties from among a parcel found 
in Clay above the great Oolite at Bradford and Pickwick, 
