CONCHIFERA. 737 



ment external, penetrating partly internally into a groove. Hinge 

 callous, edentulous. 



LAMARCK, who first made this genus known, thought that it was found 

 in the sea. It was placed in the neighbourhood of the Oysters, from which, 

 however, the shell differs by the two muscular impressions. Since that 

 time these conchifers were found in the Nile by the traveller CAILLAUD. 

 The animal was afterwards described and figured by RANG and QUOT. It 

 agrees, as RANG remarks, with that of Unio and Anodonta, so that in fact 

 the Etherice might be shortly characterised as irregular Anodonta with one 

 of the two shells attached. 



Comp. LAMAECK Ann. du Museum, x. pp. 398 408, PL 29 32 ; FE- 

 RUSSAC Notice s. 1. Etheries trouvees dans le Nil, Mem. de la Soc. d'Hist. 

 not. de Paris, I. 1823, pp. 353 372; RANG et CAILLAUD Mem. sur le genre 

 Etherie et descr. de son Animal, Nouv. Ann. du Museum, in. 1834, pp. 128 

 144, QUOY in LESSON Illustr. de Zoologie, PL 58, 59 (1835). 



Sp. Etheria Lamarckii FEBUSS., Eih. elliptiea LAM. (and Eth. trigonula 

 ejusd.), Ann. du Mus. x. PL 29, 30, fig. i, BLAINV. Malac. PL 70 bis, fig. 

 i, &c., GUERIN Iconogr., Mollusq. PL 26, fig. 8. 



All the known species live in fresh water in Africa, and would seem, 

 with Iridina, to represent the Uniones so numerous in America, which 

 are not abundant in Africa. 



Family IX. Carditacea. Mantle cloven. Foot compressed, 

 ulcate, not byssiferous. Tentacles around the mouth divided into 

 everal lobes. Shell regular, free, inequilateral, equivalve. Two 



muscular impressions remote. Teeth of hinge mostly two, in some 



a single tooth, the anterior being obsolete. 



Cardita BRUG. (exclusive of species), DESK A YES (Cardita and. 

 Venericardia LAM.). Shell suborbicular, transverse or oblique, 

 often costate longitudinally. 



An historical review of the genus Cardita, and of the modifications it 

 has undergone, was given by DESHAYES Encycl. meth., Vers. II. 1830, pp. 

 194 196. All the species now living are marine, mostly small or only of 

 moderate size. The fossil species are numerous, especially in the calcaire 

 grossier, as Cardita imbricata, Venericardia imbricata LAM., LISTEE Hist. 

 Conchylior. Tab. 497, BLAINV. Malacol. PL 68, fig. 3, DESHAYES Conchy- 

 liol. PL 3 r, fig. 6, &c. 



Family X. Chamacea. Mantle excised with a middle aperture 

 'or the foot, and furnished with two distinct foramina in the tentacu- 

 ate margin (trachea of mantle and trachea of gills), elsewhere 

 VOL. I. 47 



