578 MAGASINJJ. 



In this genus the apophysary system is anchor- shaped, 

 consisting of an elevated central plate, to which are affixed 

 two short lamella? ; a single species only is known, dredged 

 at Rio in thirteen fathoms by J. Macgillivray. 



Genus MEGERLIA, King. 



Shell transversely oblong, with a wide and rather straight 

 hinge-line ; area distinct ; foramen incomplete. Loop 

 rather short, reflected, triply attached, once to the hinge- 

 plate and twice to the septum, by processes from the crura 

 and also from the reflected portion of the loop. 



Syn. Kingena, Davidson. Ismenia, King. 



Ex. M. truncata, Linnaeus, pi. 131, fig. 3. Shell, M. 

 truncata, fig. 3, a, 3, b. 



In this genus two short, central, diverging branches arise 

 frorn the extremity of the longitudinal septum and support 

 the calcareous loop, the riband-shaped lamella? of which, 

 first attached to the crural base, afterwards become fixed to 

 the diverging branches of the septum, and then proceed 

 nearly parallel to one another until they form a reflexed 

 loop, which also gives off two processes which affix them- 

 selves to the median crest. 



Species of Megerlia. 

 pulchella, Soiv. truncata, Linn. 



Genus KRAUSSIA, Davidson. 



Shell sub-circular, with a nearly straight hinge-line; 

 beak truncated, laterally keeled ; foramen large and round ; 

 deltidia small, disunited; hinge-area flat; dorsal valve 



