CONCHIFERA. 47\ 
In Derbyshire the mussel-band is wrought, like marble, into 
Vases, 
? Myoconcua, J. Sowerby. 
Type, M. crassa, Pl. XIX., Fig. 25. (Mya, mussel, concha, 
shell. ) 
Shell oblong, thick, with nearly terminal depressed umbones ; 
lhgament external, supported by long, narrow, appressed plates ; 
hinge thick, with an oblique tooth in the right valve; anterior 
muscular impression round and deep, with a small pedal scar 
behind it; posterior impression large, single; pallial line 
simple. 
This shell, which is not nacreous inside, is distinguished from 
any of the Mytilide by the form of its ligamental plates and 
muscular impressions; the hinge-tooth is usually overgrown 
and nearly obliterated by the hinge-margin, as in aged examples 
of Cardita orbicularis and Cypricardia vellicata. 
Fossil, 26 species. Permian—Miocene. (D’Orb.) Europe. 
Sub-genus. ? Hippopodium (ponderosum, Sowerby), Coneybeare. 
Lias, Europe. Shell oblong, thick, ventricose ; umbones large ; 
ligament external; ventral margin sinuated; hinge with one 
thick, oblique tooth in each valve, sometimes nearly obsolete ; 
pallial line simple; anterior muscular scar deep. This shell 
appears to be a ponderous form of Cypricardia or Cardita ; it is 
a characteristic fossil of the English Lias, but only very aged 
examples have been found. 
CarpDITA, Bruguiére. 
Synonyms, Mytilicardia and Cardiocardita (ajar), Bl. Arcinella, 
Oken. 
Type, O. calyculata, Pl. XX., Fig. 5. 
Etymology, cardia, the heart. 
Shell oblong, radiately ribbed; ligament external; margins 
toothed; hinge-teeth 1.2, and an elongated posterior tooth; 
pallial line simple; anterior pedal scar close to adductor. 
Animal with the mantle-lobes free, except between the 
siphonal orifices; branchial margin with conspicuous cirri : foot 
rounded and grooved, spinning a byssus; labial palpi short, 
triangular, plaited ; gills rounded in front, tapering behind, and 
united together, the outer pair narrowest. 
C. pectunculus, Bruguiére, (Mytilicardia, Blainville), has an 
anterior tooth. C. concamerata, Bruguiére, found at the Cape, 
has a remarkable cup-like inflection of the ventral margin ot 
each valve. 
