CARD IT A. 



Plate I. 



Genus Cardita, Bruguiere. 



Testa aquivalvis, vald'e inaquilateralis , vel elongata, vel 

 orbicularis, costis ab umbonibus ad marginem diver- 

 gentibus, margine sapisshne crenulato. Car do den- 

 tibus in valvd altera duobus obliquis, altera elongato, 

 crasso, altero subrecto, breviusculo ; in altera dente 

 unico elongato, crasso, obliquo. Pal/ii impressio 

 muscularis Integra. Ligamentum externum. 



Shell equivalve, very inequilateral, either long or orbi- 

 cular, with ribs radiately diverging from the urn- 

 bones to the margin, which is, with rare exception, 

 crenulated. Hinge : in one valve are two oblique 

 teeth, one of which is thick and elongated in pro- 

 portion to the length of the shell, whilst the other 

 is straight, and rather short ; in the other valve is 

 a single oblique elongated tooth. Muscular im- 

 pression of the mantle entire. Ligament external. 



The genus Cardita was introduced by Bruguiere in 

 the ' Encyclopedie Methodique' for the purpose of dis- 

 tinguishing all the Chama of his great predecessor, 

 whose shells are of regular growth and live free or un- 

 attached. This seemingly natural group was still 

 however susceptible of division ; Lamarck distributed it 

 into the following genera, Isocardia, Cypricardia, Car- 

 dita and Venericardia, and it is the two last of these 

 united under the common title of Cardita that 1 have 

 now to illustrate. 



The first peculiarity that invites attention, both in the 

 Cardita; and Cypricardia, as distinguished from the beau- 

 tiful cordiform symmetry of the Isocardia, is the great 

 dissimilitude between the anterior and posterior portions 

 of the shell, the former being remarkably short and con- 

 tracted, whilst the latter is always more or less elon- 

 gated or rounded. The Cardita are rather numerous in 

 species, and exhibit all the modifications of growth be- 

 tween the narrow elongated form of the C. pectunculus 

 and the globose orbicular proportion of the C. Cuvieri ; 

 the Cypricardia are inconsiderable in number, and mostly 

 elongated. 



It may be as well perhaps to consider the characters 

 by which these genera differ from each other. The 

 Cardita have two simple, thick, oblique teeth in one 

 valve, one of which, varying in length according to the 

 elongated proportion of the shell, interlocks with a 

 single oblique plait in the opposite valve. The denti- 



tion of the Cypricardia, on the other hand, is of a more 

 complicated character, there being three cardinal teeth 

 just below the umbone in each valve, together with a 

 long flexuous lateral tooth. The shells of these genera 

 seem to differ moreover both in colour and chemical 

 composition, and Deshayes anticipates a difference in 

 the animals of sufficient importance in his estimation to 

 warrant their being arranged in separate families. The 

 Cardita have the lobes of the mantle entirely disunited, 

 as in the Uniones, whilst in the Cypricardia, he has 

 every reason to believe, they are joined posteriorly as in 

 the Cardia. 



Species 1. (Mus. Cuming.) 

 Cardita calyculata. Card, testa oblongd, a/bidd ,■ 

 latere postico sinuato ; costis octodecim, subti/issim? 

 imbricato-squamosis, costarum interstitiis lineatis,non 

 crenatis ; margine obsolete plicato. 

 The bud-shaped Cardita. Shell oblong, whitish, 

 posterior side sinuated ; ribs eighteen in number, 

 each covered with a row of very finely imbricated 

 scales ; lateral tooth rather sharp ; margin obso- 

 letely plaited. 

 Bruguiere, Enc. Meth. vers, p. 408. 

 Chama calyculata, Linnaeus. 

 Cardita sinuata ?, Lamarck. 

 Hab. Mediterranean. 



This and the C. variegata appear to have been con- 

 founded together by Linnseus, Born, Chemnitz, and all 

 the early writers under the common title of C. calyculata. 

 Bruguiere was the first to note the important difference 

 that exists between these species : he set apart the shell 

 described above under the old specific title of calyculata, 

 and applied a new name, variegata, to the other. This 

 order was however reversed by Lamarck ; the latter 

 species was described by that conchologist under the 

 name of C. calyculata, and the error has been incau- 

 tiously perpetuated both by Sowerby and myself; by 

 Sowerby in 'The Genera of Recent and Fossil Shells,' 

 and bv myself in the ' Couchologia Systematica.' The 

 ribs in this species are fewer in number ; the scales 

 which surmount them are much more numerous, smaller, 

 and more finely imbricated ; the interstices between the 

 ribs are wider and not crenulated ; and the shell is of 

 one uniform pale yellowish-white colour, with little or 

 no indication of any dark spots. 



June 1S43. 



