812 EXPLANATION OV THE PLATES. 



Plate 22. 



64. Generative organs of the American oyster. P, labial 



palpi ; H, heart ; Mits, adductor muscle ; 3It^ mantle ; 

 G, branchise ; 6^e%, generative organs ; od, oviduct. 

 (Ryder), 124 



65. Anatomj^ of the American oyster. H, hinge ; lig^ liga- 



ment ; A^ lower margin of shell ; G, gills ; CI, cloaca ; 

 F, vent ; Mus, adductor muscle ; /, II, III, its areas ; 

 & to c, upper side of the animal ; c to a, lower side ; 

 Mt, mantle ; tent, tentacles ; P, palpi ; P, sp, palpal 

 space ; I, cav, gill cavity ; e, gill membrane ; men, 

 mesosoma, or lower middle portion of the body; Uc, 

 upper gill cavity ; M, mouth ; st, stomach ; ce, oesoph- 

 agus ; L, liver ; G st, crystalline stylet ; Int, intestine ; 

 Fer, pericardium ; /, Jids, double fold of intestinal 

 cavity; ve, ventricle ; au, auricle ; a o, a o' , aortse ; he, 

 branchio-cardiac vessels. (Ryder), . . 86, 105 



