Oardita.] PELECYPODA. 903 



This incubation in one group takes place in the atrium of the ovary, 

 in another in a specially developed fold of the ventral part of the 

 mantle-lobes which secretes and lines a shelly marsupium which is 

 absent in the shells of male individuals. Viviparous. 



Shell equivalve, solid, cordiform, oval or transverse, usually with 

 radial sculpture, the pedal adjacent to the anterior adductor-scar ; 

 ligament external, parivincular, resilium usually included in the liga- 

 ment ; hinge fully developed, with 1 or 2 cardinal teeth, and sometimes 

 1 or 2 laterals ; the anterior caidinal often obsolete, the posterior 

 prolonged parallel with the dorsal margin even below the ligament. 



Trias to Recent. 



KEY TO GENERA. 



A. Shell strongly radially costate. 



a. Shell elongate-quadrate ; right valve with 2 lainelliforin 



smooth parallel cardinal teeth . . . . . . CARDITA. 



b. Shell rounded-trigonal ; right valve with 3 or only 2 



transversely finely striated cardinal teeth . . VKNERICARDIA. 



B. Shell smooth. Each valve with a single cardinal and 2 pos- 



terior teeth . . . . . . . . . . VERTICIPRONTTS 



Genus 1. CARDITA (Bruguiere), Lamarck, 1799. 

 ('tirdita, Bruguiere, Enc. Meth., i, 1792, 401; Lamarck, Prodrome d'une 

 Nouv. Class. Coq., 1799, 86. Type: C. cali/culata, L. Mytilicardita , 

 Anton, 1839. Jesonia, Gray, 1840. Mytilicardia, Herrmansen, 1847. 

 Not Cardita, Morch, 1853 = Isocardia, Lam. 



Animal with a short foot and a byssus with numerous fine filaments. 



Shell elongate-quadrate, strongly radially ribbed, very inequi- 

 lateral, and with a narrow byssal gape ; lunule more or less depressed ; 

 hinge oblique ; right valve with a feeble anterior lateral and 2 long 

 lamelliform parallel cardinal teeth ; left valve with a short anterior 

 cardinal, an elongated posterior cardinal, and a small posterior lateral 

 tooth ; muscle-scars large and conspicuous ; pallial line simple. 



Distribution. -- Mediterranean, coasts of Africa, Indian Ocean, 

 Philippines, Australasia, &c. 



Fossil in the Secondary and Tertiary. 



1. Cardita calyculata, Linne, 1758. Plate 58, fig. 15. 



Chama calyculata, L., Syst. Nat., ed. 10, 1758, 692. Cardita calyculata, L. : 

 Lamarck, A.s.V., vi, 1819, 24 ; Hanley, Cat. Rec. Biv. Shells, 147, pi. 18, 

 f. 7 ; Conch. Icon., i, pi. 1, f. 1 ; Chall. Rep., xiii, 14, 210 ; Suter, T.N.Z.I., 

 xxxviii, 317. C. aviculina, Lamarck, A.s.V., vi, 1819, 26 ; Delessert, 

 Recueil de Coq., 1841, pi. 11, f. 11 ; Hanley, Cat. Rec. Biv. Shells, 148, 

 pi. 18, f. 24; Index, 92. C. excavaia, Deshayes, P.Z.S., 1852 (1854), 

 100, pi. 17, f. 1-3 ; Chall. Rep., xiii, 210. Mi/tilicardw excavata, 

 Deshayes, C.M.M., 76 ; Hutton, J. de Conch., xxvi, 52 ; M.N.Z.M., 160 ; 

 M. tasmanica, T. -Woods, P.R.S. Tas., 1875 (1876), 161 ; Hutton, P.L.S. 

 N.S.W., ix, 257. M. calyculata, L. : Pritchard and Gatliff, P.R.S.. Vic., 

 xvii (n.s.), 234. 



Shell elongate-quadrate, very inequilateral, inflated, with radiate 

 scaly ribs, sinuated and gaping below. Beaks near the anterior end, 

 small, compressed, approximated. Anterior end very short, subtrun- 



