CONCHlfERA. 471 



In Derbyshire the mussel-band is wrought, like marble, into 

 Vases. 



? Myocoxcha, J. Sowerby. 



Tijpe, M. crassa, PL XIX., Fig. 2b. {My a, mussel, concha^ 

 shell.) 



Shell oblong, thick, with nearly terminal depressed umbones ; 

 ligament 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 Mytilidoe, 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 Cypriccn-dia vellicata. 



Fossil, 26 species. Permian — Miocene. (D'Orb.) Euro]3e. 



Suh-genus. ? Hijypopodium (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. 



Cahdita, Bruguiere. 



Synonyms^ Mytilicardia and Cardiocardita (ajar), Bl. Arcinella, 

 Oken. 



Type, C. calyculata, PL XX., Pig. 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. pedunculus, Bruguiere, [Mytilicardia, Blainville), has an 

 anterior tooth. C. concamerata, Bruguiere, found at the Cape, 

 has a remarkable cup-like inflection of the ventral margin ot 

 each valve. 



