16 COMPARATIVE AXATuMY chai'. 



portions of each filament are similarly united (cf. Fig. SS. p. 92). Fain. Pectinidse: 





% 





//; 



Fio. 23.— Pecten Jacobaeus, ventral aspect, shell opened. The mantle cleft Is seen betwetu 

 the fringes of tlie mantle, which are beset with numerous tentacles and eyes (after Leuckart and 

 Nitsche, Zool WamltafLln). 



Fig. 24.— Anatomy of the Oyster (Ostrea edulis), right aspect (after Mobius, Leuckart, :uid 

 Nitsche, Znol. U'tindtafdn). hi; Gills ; Pn, posterior mantle nerve ; .»■, xi, apertures of the cavities 

 between the fused plates of the two left gills ; .17, large adductor muscle ; a, anus ; .V»i, posterior 

 portion of the adductor muscle ; Pa, mantle ; P, pericardium ; V, heart ; go, gonad (hermaphrodite 

 gland) ; d, intestinal canal ; I, digestive gland Giver) ; o, mouth ; os, osy oral lobes (labial palps) of 

 the left side ; Cg, cerebral ganglion ; a, kidney ; hn, branchial nerve ; Vg, visceral ganglion ; Pj, abdo- 

 minal process ; Piii, nerve of the pallia! edge ; m, stomach, with the apertures of the digestive gland. 



Mouomyarian with mantle entirely open, and eyes at its edge. Without .siphons. 

 Foot small and linguitbrm. Valves of the shell equal or unequal. Capable of 



