189 



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 distinct 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 neigh- 

 bourhood of Paris : C. scute llaria, C. demisulcata, C. nitidula, C.polita, C. l&- 

 vigata, C. teliinaria, C. elegans, C. deltoidea, C. corbulina. 



In the Essex and Suffolk bank is a fossil shell of this genus : it appears 

 to resemble, in its specific, as well as in its generic characters, Venus exo- 

 leta, 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 hi- 

 therto 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 ; 

 arid 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 Tdlina cornea. The exotic 

 Cyclades, and particularly those of Asia, are very large,v 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 C. deperdita, 

 the only fossil species mentioned by Lamarck. Like this species, the 



