PART II. MAGROTRACHIA. SAXICAVIDjE. 375 



Cleidothcerus Stuchbury. Shell resembling Chama, but 

 somewhat pearly ; hinge with an " internal, testa- 

 ceous, curved appendage/' inserted in a depression 

 within each of the bosses. 



C. chamoides. Sow. Man. f. 75. 



Diceras Lam. Somewhat resembling Isocardia ; but 

 the bosses are excessively produced and turned dif- 

 ferent ways. Fossil only. 



D. arietinum. Sow. Gen. f. 1. 



Myochama * Stuchbury. Shell irregular, smooth, at- 

 tached by the lower valve ; umbones central ; cardinal 

 teeth small, -, between which is an internal shelly 

 appendage, attached to a horny cartilage. 



M. anomiodes. Sow. Man. f. 73. 



CARDITA t Lam. Shell 

 free, cardiform, or 

 sub-transverse, rib- 

 bed ; cardinal teeth 

 A or |, lateral \ ; re- 

 presenting Ceirdium. 



(fig- 121.) 



C. sulcatus. Sow. Gen. f. 3. imbricatus. Ib. f. 4. 

 calyculatus. Ib. f. 1,2. oblonga. Ib. 



FAMILY SAXICAVIMS. 



Animal perforating ; shell often irregular ; lateral teeth 



none ; cardinal teeth variable or obsolete. 



SAXICAVA Lam. Shell transversely oval, irregular, 

 gaping at one or both ends ; ligament external ; teeth 

 obsolete. (%. 122. a, e.) 



S. rugosa. Sow. Gen. f. 1 4. 



Petricola Lam. Shell transversely oval or oblong ; the 

 valves gaping ; cardinal teeth variable, but always 

 present ; lateral teeth none (fig. 122. 6, c, rf.) 

 P. dactylus. Sow. Gen. f. 3. ochroleuca. Ib. f. 4. (6. ) 



* Affinities uncertain. 



f Including I'enericardia and Cypricardia Lam. I fig. 121.), the latter 

 seems an aberrant Cardita. passing into Coralliophaga. 



