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base ; with a distant one under the cordiform depression, in one valve, 
and a little pit for its reception in the other. 
The general form of these shells agrees with that of the shells of the 
preceding genus ; but the isolated tooth, and the corresponding pit, 
afford characters certainly sufficient for disposing them under a dis- 
tinct genus, under which Lamarck places V. meretrix, punctata, 
lusoria, Iceta , pectinata, tigerina, chione, and indeed all those which 
have a tooth distinct from the cardinal ones. He particularizes nine 
species found fossil in the neighbourhood of Paris : C. Scutellaria, C. 
demisulcata, C. nitidula, C. polita, C. Icevigata, C. tellinaria, C. 
elegans, C. deltoidea, C. corbulina. 
In the Essex and Suffolk bank is a fossil shell of this genus : it ap- 
pears to resemble, in its specific, as well as in its generic characters, 
Venus exoleta, Linn. List. Conch, t. 292, Fig. 128. 
CXVII. Cyclas. An ovato-transverse bivalve, not inflected on the 
fore part : the hinge with three hinge-teeth and two lateral ones, 
compressed, and rather remote. 
The shells of this genus are chiefly river shells, some of which have 
hitherto been placed under the genus tellina, and others under Venus : 
but having no fold on their anterior part, they are not referable to the 
former ; and having two lateral teeth, they cannot be placed under 
the latter genus. 
Lamarck describes the Cyclades of Europe as small, thin, and, as it 
were, horny, with the hinge-teeth not very distinct. It is from these 
shells that Linnaeus has taken his species tellina cornea. The exotic 
Cyclades, and particularly those of Asia, are very large, and have 
their hinge-teeth very distinct, and very often bifid. Amongst these 
he places Venus coaxans, V. islandica, and several other shells, which 
have been hitherto placed under the genus Venus. 
Very few other bivalves are to be found in that vast stratum of 
shells extending so widely from Woolwich, except a shell, which I 
think is decidedly referable to this genus, and perhaps to the species 
