94 CONCHIFERA. DIMYAIRA. 



of Britain, in cavities of limestone, and the roots of fuci Pen. 



Brit. Zool. iv. pi. 67, fig. 1. 



Dr Fleming is of opinion that these two species, as well as the M. prcecisus and 

 plicatus of Montagu, are varieties of the same shell ; and that the animal possesses 

 both the power of burrowing in limestone, and of affixing its shell to other bodies, 

 by means of a byssus. We possess specimens of all the varieties ; but from the shells 

 of some being constantly found rough and foliaceous, or lamellar, while others of 

 equal size are smooth, and the spinous ridges much developed, it may be doubted 

 whether they do not form at least two species. One fossil species is found in the 

 carboniferous limestone of the Forth coal-field Fhminefs Brit. An. 162. 



Gen. 16. CYPRICARDIA, Lam. Chama, Lin. 

 Shell free, equivalve, inequilateral, elongated obliquely or trans- 

 versely ; three primary teeth under the beaks, and one late- 

 ral tooth. 



C. Guinaica, Lam. Shell oblong, obliquely angulated, with decus- 

 sated striae, compressed before, and the apex rounded ; colour 



yellowish white. 2 inches long. Inhabits coasts of Guinea 



Ckem. vii. pi. 50, fig. 504, 505. 



C. angulata, Lam. Shell oblong, obliquely angulated before, with 

 decussated striae, the transverse furrows largest ; obliquely trun- 

 cated laterally, and carinated ; colour white. Inhabits coast of 

 New Holland. Lam. vi. 1, 28. 



Fossil species of this genus are found in France near Caen. 



Gen. 17. CARDITA, Lam. Chama, Lin. 

 Shell free, regular, equivalve, inequilateral ; hinge with two un- 

 equal teeth, the one short, straight, placed under the beaks ; 

 the other oblique, marginal and elongated. 



The shells of this genus are all marine. Fossil species are found in Britain in 

 oolite and green-sand. 



C. sulcata, Lam. (C. antiquata, Lin.) Shell subcordate, tesselated 

 with red, white, and brown, transversely striated, with longitu- 

 dinal convex ribs ; posterior depression cordiform. 1 inch long. 

 Inhabits Mediterranean sea. Lister, pi. 346, fig. 183. 



C. ajar, Lam. Shell subcordate, red, spotted with white or yellow, 

 with longitudinal angulated ribs, and the furrows tuberculated ; 

 posterior depression round. 1 inch long. Inhabits coasts of Africa. 

 Lam. vi. 1, 22. 



* Shell longer than broad, 



C. phrenitica, Lam. Shell oblong-ovate, compressed and rounded 

 above, with longitudinal furrows and transverse striae ; margin 

 crenated behind ; colour reddish-brown. 2^ inches long. Inha- 

 bits seas of New Holland. Chem. vii. pi. 50, fig. 502, 503. 



C. nodulosa, Lam. Shell oblong, trapezoidal, gibbous, reddish, with 

 sixteen rounded nodulous ribs ; margin entire. 1^ inch long. In- 

 habits seas of New Holland. Lam. vi. 1, 25. 



Gen. 18. CARDIUM, Lam. Lin. 

 Shell equivalve, subcordiform, with protuberant beaks ; valves 



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