MOLLUSC A. 43 



and richly ciliated. By the fusion of the two inner gill-lamellae 

 through the hinder third of their extent, the mantle-cavity is 

 divided into a superior or anal chamber, into which the anus 

 opens, and an inferior or pallial chamber. The anal chamber, 

 indicated in the preparation by a white bristle, corresponds to 

 the exhalent siphon. Anterior to this union the two laminae are 

 free, but are united to the body-mass anteriorly to this. On 

 each side of the mouth is a pair of lamellar labial palpi. 



67. A vertical section of an Anodon. The section has been 

 taken through the heart and intestine, the organ of Bojanus, 

 the visceral mass, and the foot. A white bristle has been in- 

 serted into the ventricle, through which the intestine is seen to 

 pass. Immediately beneath the heart a black bristle is inserted 

 into the great dorsal sinus, and right and left of this, a white 

 bristle has been placed in the secretory portion of the organ of 

 Bojanus, which overlies the excretory portion. The preparation 

 also shews the relation of the mantle and the two pairs of gills 

 to the median visceral mass. The three inferior bristles indicate 

 sections of the intestine which have been cut through in the 

 specimen. 



68. The same, prepared to shew its digestive system. 

 The right lobe of the mantle and the right gill have been 



removed, and part of the muscular foot and liver cut away to 

 shew the convolutions of the alimentary canal, which has been 

 filled with a light blue injection. A blue glass rod has been 

 placed in the mouth. 



69. The same, prepared to shew the two muscles which 

 serve to draw the valves of the shell together (the anterior 

 and posterior adductor muscles). The strings by which the 

 proportion is suspended are attached to the posterior extremity 

 of the shell. Rolleston, p. 54. 



70. The same, to shew its nervous system. 



The animal is suspended on mica with its mouth upwards. 

 Part of the muscular foot has been removed on the left side to 

 shew the pedal ganglion in situ. Part also of the organ of 

 Bojanus has been cut away to shew the nervous commissure 

 connecting the cephalic with the parieto-splanchnic ganglion, 

 and posteriorly the two inner lamellae of the two inner gills 

 have been separated so as to shew the commissure last men- 



