42 
CARDIUM Plumstediamim, 
TAB. XIV .—Right and left hand upper figures . 
Spec. Char. Sub cordate., smooth; anterior part 
longitudinally furrowed. 
It has so much of the outer contour of the shell above, 
that it has been doubted whether they may not be the same 
species, the outside, however, does not seem at any time to 
have had the rising concentric lines, only the irregular and 
less distinct striae of growth ; and the lateral longitudinal 
pleated furrows cover but one fifth of the surface, and are 
terminated at the edge of the shell by longer and sharper 
serratures. The serratures round the other parts of the shell 
are not seen from the outside. 
This is a rare species, but I was so lucky some time since, 
as to procure the specimens figured, and some smaller ones. 
It is fortunate when the inside of the shell is understood 
perfectly, on account of its preventing doubt as to the genus 
to which it belongs. The specimens are found in a loose 
mixture of sand, fragments of shells and gravel, above a 
stratum of gravel and covered by several layers of different 
sized gravel, one or two of which have such large pebbles, 
that they must have been laying very quiet when they 
were deposited, or they would have been inevitably crushed 
to pieces. The texture of shells found in gravel or clay is 
extremely delicate, and will scarcely allow the handling of 
them, indeed the contrast of a warm hand has made some 
specimens fall to pieces. Some "of my friends soak them in 
Linseed oil to strengthen them, which protects them when 
dry, but gives them a disagreeable odour. I should ima- 
gine that to impregnate them with a little gum water would 
in most instances be pleasanter. 
