COXCniFERA. 



437 



Family YII. — Chamid.e. 



Shell inequivalve, thick, attached ; beaks sub-spiral ; ligament 

 external ; hinge-teeth 2 in one yalve, 1 in the other ; adductor 

 impressions large, reticulated ; pallial line simple. 



Animal with the mantle closed ; pedal and siphonal orifices 

 small, sub-equal ; foot very small ; gills two on each side, very 

 unequal, united posteriorly. 



Chama (Pliny), L. 



Example, C. macrophylla, PI. XYIII., Figs. 8, 9. 



Synonym, Arcinella, Schum. 



Shell attached usually by the left umbo ; valves foliaceous, the 

 upper smallest ; hinge-tooth of free valve thick, curved, received 

 between two teeth, in the other; adductor impressions large, 

 oblong, the anterior encroaching on the hinge-tooth. 



Animal with the mantle-margins united by a curtain, with 

 two rows of tentacular filaments ; siphonal orifices wide apart, 

 branchial slightly prominent, fringed, anal with a simple valve ; 

 foot bent, or heeled ; liver occupying the umbo of the attached 

 yalve only ; ovary extending into both mantle-lobes, as far as 



Fig. 223. Right side. Fig. 224. Left side. 



Fig. 223. Right side, with the umbonal portion of tlie mantle removed. 



Fig. 224. Left side, showing the relative extent of the liver and ovarium. 



a, a, adductors ; m, pallial line ; e, excurrent orifice ; b, branchial ; /, foot and 



pedal oiifice ; p, posterior pedal muscle ; t, palpi ; g, gills (contracted) ; /, liver ; o, 



ovarium ; d, dental lobes. 



the pallial line ; lips simple, palpi small and curled ; gills deeply 

 plaited, the outer pair much shorter and very narrow, furnished 

 with a free dorsal border, and united behind to each other, and 

 to the mantle ; adductors each composed of two elements. 



