134 
gives it a triangular aspect. The ears are small and con- 
tinued along the sides. 
I found this some years since at Chute Farm near War- 
minster, in the green sand, a place that afforded me an 
extraordinary variety on a small piece of land. The spe- 
cimens vary a little, and have more or less Carbonate of 
Lime in them, filling up betwixt the calcedonic infiltration, 
which looks like a little worm shell or Serpula, but on 
inspection discovers a sort of stalagmitical form of the 
calcedony in cirples, rings, or drops. 
DIANCHORA lata. 
TAB. L XXX.— Fig. 2. 
Spec. Char. Semicircular, beak rising; free valve 
plain. 
The obliquity of this species is scarcely to be observed ; 
the lines of growth being slightly marked, and the gentle 
convexity of its form, added to the indistinctness of the few 
striae upon its surface, and the sharpness of its edge, give it 
a peculiar plainness of character. 
This is from the Chalk near Lewes, by favour of Mr. 
Mantell; it is but little known, I believe, at present in 
Chalk, and it differs from any I have hitherto seen in other 
strata or formations. 
