73 
EMARGINU LA 5 Lamarck • 
Gen. Ci-iar. Univalve,, obliquely conical, vertex 
inclined; anterior or posterior margin, with a 
single deep notch or fissure. 
EMARGINULA crassa. 
TAB* XXXIIL — Upper figures. 
Spec. Char. Oval, obtusely conical, furrowed; 
with four or five striae between each furrow; 
fissure wide. 
This shell is remarkably thick, and the lines of growth 
are marked across the striae. The fissure is filled up for 
half its length by a thinner continuation of the shell. 
I conceive this to be a species hitherto undescribed; it 
was found in the Crag near Ipswich, by Mrs. Cobbold, 
whose zeal for science prompted her to send me the fine 
specimen from which this figure is taken. I have not seen 
another specimen, but consider this a full grown shell, for 
towards the margin the lines of growth become very strong 
and irregular, which from analogy may be supposed to 
point , out the usual size. There is besides an additional 
piece round the edge, produced as it were by an extra 
effort of growth, similar to that in many old shells. The 
substance of the shell is about as hard as plaister of paris 
cast, without any appearance of crystallization, but remains 
of a glossy smoothness in some of the interior parts; the 
outside looks like that of a dead, decaying, bleached shell; 
it is a little stained by oxided Iron. Some animals have 
formed holes in it, and there are the zigzag grooves of some 
kind of Serpula remaining in it. 
