16 
CORBULA revoluta. 
TAB. CClX.—Figs. 8 to 13. 
Syn. Tellina revoluta. Brocchi 516. tab . 12./. 6. 
Spec. Char. Transversely oblong', tumid, trans- 
versely furrowed ; anterior side produced, trun- 
cated, with a carina running* to the beak ; mar- 
gin of the larger valve prominent, inflected; 
beaks unequal. 
Var. (costata) transverse furrows few, deep ; 
anterior side rather pointed, (figs. 11, 12, 
and IS.) 
The width is frequently twice the length; the edge of 
the lesser valve is almost wholly enclosed in the larger, 
the margin of which at the front is expanded, and rather 
bent inwards, whence the name given by Brocchi. The 
anterior side of the larger valve is extended in the form of 
a truncated beak, but liable, as well as the general form, 
to such irregularities as are common to shells which inha- 
bit holes and cracks in rocks ; the furrows are numerous 
and sharp, except in var. /3, which has them rounded, and 
the ridges between them sharp. The beak of the larger 
valve is very gibbose in old shells. 
From Barton Cliff by favour of the Rev. Mr. Bingley, 
in plenty ; some have the furrows so irregular that it is 
difficult to say to which variety they belong, otherwise I 
should have been led by the general form to consider the 
var. jS a distinct species. 
