XII 



PHYLUM MOLLUSCA 



639 



together to the sides of the visceral mass a little below the origin 

 of the mantle : the inner lamella of the inner gill is also attarlu-d 

 to the visceral mass in front (A), but is free further back (B). The 

 gills are longer than the visceral mass, and project behind it, below 



rcb 



3 



FIG. 530. Anodonta cygnea. Three transverse sections. <<>'. auricle : '//. urinary bladder: 

 t./t. til. external gill : .//. foot ; i. 1. j. inter-lamellar junction; i,tt. intestine : int. (>l . internal 

 gill; M. kidney ; k. n. Iveber's organ; lit. ligament; <. mantle; />. ml. imsterinr aiUluctor ; 

 JK: pericardium; /</. rectum; . ///. <: supra-branehial chamber; sh. shell; i<i. typhlosole ; 

 v. !ii<. visceral ganglion. (After Howes, slightly altered.) 



the posterior adductor (C), as far as the posterior edge of the 

 mantle : in this region the inner lamellse of the right and left 

 inner gills are united with one another, and the dorsal edges 

 of all four gills constitute a horizontal partition between the pallia! 

 cavity below and the exhalant chamber or cloaca above. Owing 



