C A R D I U M. 



Plate I. 



i ri nus < ' iimn m, LinniEus. 

 Testa mquivale'is, plus minusve hieequilateralis, subcordata, 

 umbonibus prombiulis, latere postico interdum hiante; 

 plerumque costata, costis nh umbonibus symmetrica di- 

 vergentibus, sapissime squamatis aid spinosis; vaharum 

 i«s crenulatis, i/derclaiidentibus. Cardo : den- 

 tibus in utrdque ruin! quatuor, duobus centralibus, ob- 

 liquis, approximatis, cruciatim intersertis, duobus later- 

 remotis. rutin impressio muscularis integra. 

 Ligamentum breve, extt mum. 

 Shell equivalve, more or Less inequilateral, somewhat heart- 

 shaped, umbones prominent, posterior side sometimes 

 gaping; generally ribbed, ribs diverging symetrically 

 from the uiribones, most frequently aimed with scales 

 or spines; margins of He- valves crenulated, inter- 

 closing with each oilier. Hinge: four teeth in each 

 valve, two central, oblique, approximated, interserted 

 cross-wise; two lateral, remote. Muscular impression 

 of the mantle entire. Ligament short, external. 

 The genus Cardium is one of the very few established 

 by Linnseus that remains entire; the specie-;, which are 

 somewhat numerous, exhibit a great similarity of form 

 throughout, anil may be generally recognised by their 

 cordjform shape, and the prominent developemenl of the 

 umbones. The most characteristic variation in form oc- 

 curs in those species winch Cuvicr distinguished b\ the 

 new title of Hemicardium, such as the Cardium hemicar- 

 dium,fragum, retusum, auriculatum, &c, but the difference 

 eainioi for a moment lie regarded of any particular generic 

 importance. Another variation worthy of mention, because 

 ii seems to indicate a difference in the characters of the 

 animal inhabitant, may be observed in those species which, 

 like the Cardia bullatum and apertum gape more or less 

 at the sides. 



The hinge of Cardium is denned with great peculiarity 

 in the typical species of the genus by the cross interlocking 

 of the central, and (lie remote arrangement of the lateral 



teeth ; but, in the aberrant S] ies, it becomes modified to 



a degree which has induced Dr. Eichwald of Moscow, ,„ 

 his" Fauna Caspio-Caucasia," to subdivide the genu- into 

 the four following subgenera, founded on certain peculiar 

 modifications in the developement of the teeth; Cardium, 

 Didacna, Monodacna and Adacna. 1 do not conceive, how- 

 ever, that these groups can lie admitted on the same prin- 

 cipal which separates, a- says Dr. Eichwald, the Uniones 

 and Anadontes; for the teeth of the I niones alone exhibit 

 as great a variation of character as those of the Cardia. 

 Some, as in the learned doctor's subgenus Didacna, have 



Octobi 



only half the usual number of central teeth developed; 

 Other species there are, like the MonodactUB, in which tin' 

 lateral teeth are obsolete; whilst the hinge of several spe- 

 cies, as in Adacna, arc almost edentulate. 



fhc chief portion of the genus Cardium has been so well 

 illustrated by Mr. Sowerby in his ' Conchological Illustra- 

 tions,' that little remains for me but to complete the mono- 

 graph as a whole. Some few additional species have pre- 

 sented themselves, but the monograph cannot be expected 

 to exhibit that interesting array of novelty winch has ac- 

 companied the genera hitherto published in this work. 



Species 1. (Mus. Cuming.) 

 Cardium serratum. Card, testa ovatd, umbones versus 

 gibbosiusculd, glabra, nitiduld, antice subobsolete striata; 



albido-fluricaiite, latere postico ririile nlriiio-jhirnh, nut 



roseo-purpurascente, maculis flavido-purpurascenttfm 

 mutatis circa umbones pallida tinctd, intus sub umboni- 

 bus fiavescetde ; marginibus intus minutissiaie serroti-<. 



The SERRATED COCKLE. Shell ovate, rather gibbous to- 

 wards the umbones, smooth, shining, anteriorly rather 

 obsoletcly striated; whitish yellow, posterior side 

 bright citron yellow or pinkish purple, palely stained 

 with pinkish-waved spots around the umbones, inte- 

 rior yellowish under the umbones; margins very mi- 

 nutely serrated w it h in . 



Lixn.i:i s (not of Gmelin), Syst. Nat. 12th edit. no. 89. 



p. 1123. 



Cardium citrinum serratum Linruei, Chemnitz, Conch. 



(,,b. vol. si. p. 194. pi. IV f. 189. 

 Cardium laoigatum, Gmelin, Lamarck, Sowerby. 

 Hub. Islands of Nevis and St. Vincent, West Indies (found 

 in sand) mud at the depth of from six to ten fathoms); 

 (i lidding. 

 1 quite agree with M. Deshayes that Chemnitz " 



mnu le Cardium lerratum de Linne." Therecorded 

 opinions of Lamarck and Sowerbj were induced probablj 

 by an error of Gmelin's, followed bj Bruguiere, in the 

 Encyclopedic Methodique. 



Species 2. (Mus. Cuming.) 

 Cardu 'a [XCarn ATi m. Cunt, testa i/ihboso-ghbosa, lon- 

 gitudinaliter costata, costis quatuor et viginli, rot/nidi*, 

 complauatis, margines versus medio 

 sis. interstitiis angustis, subprofundis, transt 

 ntis: pallide incarnata,radiis roseis transversa hie illic 



