16 COMPARATIVE ANATOMY CHAP. 



portions of each filament are similarly united (cf. Fig. 88. p. 92). Fam. Pectinidse: 



FIG. 23. Pecten Jacoboeus. ventral aspect, shell opened. The mantle cleft is seen between 

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

 Nitsche, Zool. Wandtafeln). 



Pi PV 



FIG. 24. Anatomy of the Oyster (Ostrea edulis), right aspect (after Mobius, Leuckart, and 

 Nitsche, Zool. Wandtafdii). br, Gills ; PH, posterior mantle nerve ; x, xi, apertures of the cavities 

 between the fused plates of the two left gills ; M, large adductor muscle ; a, anus ; Mm, posterior 

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

 gland) ; d, intestinal canal ; I, digestive gland (liver) ; o, mouth ; os, osj, oral lobes (labial palps)'of 

 the left side ; Cg, cerebral ganglion ; n, kidney ; bn, branchial nerve ; Vg, visceral ganglion ; P 1; abdo- 

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



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

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



