3 8o 



/ '// ) Y, UM MOT.L USC A. 



intestine, which has in part a folded wall like that of the 

 earthworm, coils about in the foot, ascends to the peri- 

 cardium, passes through the ventricle of the heart, and ends 

 above the posterior adductor at the exhalant orifice. 



Vascular system. The heart lies in the middle line on 



r. 



FIG. 189. Structure of Anodonta. After Rankin. 



a.a., Anterior adductor; c.p.g., cerebro-pleural ganglia; st.. 

 stomach; v., ventricle, with an auricle opening into it; /., 

 kidney, above which is the posterior retractor of the foot ; 

 ;-., rectum ending above posterior adductor; v.g-., visceral 

 ganglia _with connectives (in black) from cerebro-pleurals ; g. , 

 gut coiling in foot ; p.g. , pedal ganglia in foot, where also are 

 seen branches of the anterior aorta and the reproductive organs ; 

 /./., labial palps behind mouth. At the posterior end the ex- 

 halant (upper) and inhalant (lower) apertures are seen. 



the dorsal surface, within a portion of the body-cavity called 

 the pericardium, and consists of a muscular ventricle which 

 has grown round the gut and drives blood to the body, 

 and of two transparent auricles one on each side of the 

 ventricle which receive blood returning from the gills and 

 mantle. In bivalves the heart-beats average about twenty 

 per minute, much less than in Gasteropods. The colour- 



