16 COMPARATIVE ANATOMY chap. 



portions of each filament are similarly united (cf. Fig. 88, p. 92). Fani. Peotinid£e: 





Fig. 28.— Pecten Jacobseus, ventral aspect, shell opened. The mantle cleft is seen bet\\een 

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

 Nitsche, Zool. Wondtafelii). 



Fig. 24.— Anatomy of tlie Oyster (Ostrea edulls), right aspect (after Mobius, Leuckart, and 

 Nitsche, Zool. Wn adtafeln). br, Gills ; Pn, posterior mantle nerve ; ,'■, .xi, apertures of tlie cavities 

 between the fused jjlates of the two left gills ; .1/, large adductor muscle ; a, anus ; il/iu, posterior 

 portion of the adductor muscle ; iVt, mantle ; P, pericardium ; r, heart ; go, gonad (hermaphrodite 

 gland) ; tl, intestinal canal ; ?, digestive gland (liver) ; o, mouth ; os, osi, oral lobes (labial palps) of 

 the left side ; Oj, cerebral ganglion ; n, kidney ; Im, branchial nerve ; Vg, visceral ganglion ; Pj, abdo- 

 minal process ; Pui, nerve of the pallial edge ; m, stomach, with the apertures of the digestive gland. 



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

 l^oot small and linguiform. Valves of the shell equal or unequal. Capable of 



