105 



CONCHACEA. 



CONCHACEA. 



106 



Cuvier, in his last edition of the ' Regne Animal,' at the foot of his 

 definition of the Cardiacea, the fourth family of his Testaceous 

 Acephala, has the following note : " M. de Blainville en fait la 

 famille des Cmchaceet." The following is Cuvier's definition of his 

 Cardiace's : " Mantle open in front (par devant), and moreover with 

 two separate openings, one for respiration and the other for the excre- 

 ments, which are prolonged into tubes sometimes distinct, sometimes 

 united into a single mass. There is always a transverse muscle at 

 each extremity, and a foot which most frequently serves for creeping. 

 It may be regarded as a sufficiently general rule, that those which 

 have long tubes live plunged in the mud or sand. One may recognise 

 on the shell this condition of organisation by the more or less 

 developed contour (contour plus ou moins rentrant), which the im- 

 pression of the attachment of the borders of the mantle describes 

 before uniting with the impression of the posterior transverse 

 muscle." 



These definitions appear contradictory, but in reality they are 

 meant to convey the same ideas. The mouth is placed anteriorly, the 

 foot is exserted inferiorly, and the tubes open posteriorly. The fol- 

 lowing is an arrangement of the genera : 





 Hinge linear and toothless freshwater. (Rang.) 



Iridina. Animal elongated, straight, rather thick on the back, 

 thinner towards its inferior border; mantle delicate, terminated 

 anteriorly by a thick border, open from the anterior muscle to two- 

 thirds of the lower border for the passage of the foot ; borders of 

 the mantle united throughout the whole posterior part, whence spring 

 two short and unequal tubes, with no retractor muscle to the siphons ; 

 foot compressed and sharp-edged. Shell, with an epidermis, nacreous 

 or iridescent internally, tolerably thick, oval oblong, elongated, in- 

 auriculated, equivalve, inequilateral, the anterior end shorter than 

 the posterior, a little gaping at either end ; umbones small and pro- 

 jecting but little, slightly inclined ; hinge very long, linear, attenuated 

 towards the middle, often creuulated, as it were, throughout its 

 length ; ligament very long, marginal, external ; muscular impressions 

 very distinct Example, /. exotica, Lam. ; /. tlongata, Sow. 



Iridina exotica, one-third of natural size. 



Lamarck gives the rivers of warm climates as the locality. The 

 specimens were supposed to come from China. M. Caillaud found 

 them in considerable abundance in the Nile ; and from his specimens 

 preserved in spirit M. Deshayes made his examination. Mr. G. B. 

 Sowerby figures another species (' Zool. Journ.,' vol. i.), /. Nilotica, 

 obtained from Sennaar by M. Caillaud, and sent to England by M. 

 D'Audebard. It very much resembles the species given here as an 

 example, but its hinge margin is not crenulated or dental ed. M. Des- 

 hayes, in his last edition of Lamarck, makes it identical with 

 /. exotica, Lam. and Desh., Anadonta exotica, Blainv., and Le Mutel, 

 A dan son. 



Hinge with Teeth. 



a 

 Regular : Hinge-Teeth lateral and wide apart (marine). 



Cardium [CARDICM]. The species are numerous, and some grow 

 to a very large size. M. Deshayes, in his edition of Lamarck, gives 

 forty-eight, including llemicardium, a form which Cuvier proposes 

 to separate from the others, comprehending the species with com- 

 pressed valves strongly carinated in the middle, observing that it is 

 difficult to suppose that the animal is not modified in unison with 

 thin singular conformation. M. Rang corroborates Cuvier's observa- 

 tion, from the examination of many living individuals of Cardium 

 na, the type ; but M. Deshayes considers that the form can only 

 be admitted as a section. 



De Blainville divides the genus into the following sections : 



1 . Species more or less gaping posteriorly, and with the ribs of the 

 shell as large as the channelings. Example, Cardium exoticum. 



2. Species not gaping, and with the ribs as large as the channelings. 

 Example, C. tuberculatum. 



8. Species not gaping, with the ribs larger than the channelings. 

 Example, C. edule. 



4. Smooth or almost smooth species. Example, C. elongatum. 



i whose anterior side is very short and nearly flat. Example, 

 'tcardium. 



ml species have been added to this genus from the collection 

 of Mr. ('inning. 

 The specie* of Cardium are found fossil. 



1. Hinge of Curdiitm tlongatum, natural size. 2. Oardium (Hemicarditim) 

 Carduta, natural size ; spotted variety. 



Deshayes in his Tables gives fifty-three living species and thirty-nine 

 fossil (tertiary), and C. ringent, C. ciliare, C. echinatum, C. eulcatum, 

 C. edule, C. tuberculatum, and C. planatum, as both living and fossil 

 species (tertiary). Of the recent species M. Deshayes, in his edition 

 of Lamarck, where they are given as forty -eight, considers 0. Indicum, 

 C, ringens, C. echinatum (of which last he makes C. tuberculatum to be 

 only a variety), C. luicatum, and C. edule (common cockle) as identical 

 with fossil species described by Brocchi and others under different 

 names. The fossil species he makes amount to thirty. Of these he 

 refers C. echinatum to its living analogue, C. Burdigalinum to the 

 recent C. Indicum, C. rhomboides to the recent C. edule, and considers 

 C. diluvianum, Lam., as identical with C. hians, Brocchi. The fossils 

 occur in nearly all the fossiliferous strata from the Supracretaceous 

 to the Grauwacke group, and appear to be most abundant in the Crag, 

 London Clay, and Greensand and the contemporaneous beds. 



Capta. Animal with the mantle considerably open at its ante- 

 inferior border for the passage of a compressed and very large foot : 



Capua Bi-aziliens!s. 



tubes separated and of considerable length, with tentacular papilla; 

 at their orifices. Shell transverse, equivalve, inequilateral, not gaping ; 



