242 ZOOLOGY. 



in this species. The mouth is situated in front of the foot 

 and at the base of the head-lobe, and is bounded by large puck- 

 ered swollen lips. Cutting down from between the tentacles, 

 a large buccal mass, the pharynx, is exposed. The mouth- 

 cavity is roofed with two broad quadrant-shaped, flat thin 

 teeth, with the free-edge serrated. On the floor of the 

 mouth lies the "tongue," or lingual ribbon (Odontophore), 

 which is folded once on itself, and is a thin band composed 

 of seven rows of teeth, those forming the two outer rows 

 long and much curved, those of the central row being stout 

 and three-toothed. The long slender oesophagus is tied 

 down, near its middle, by the brain (supraoesophageal gan- 

 p-lion) ; just behind and beneath which are the two large 

 Esophagus suddenly dilates into a 

 >( h-like pun eh, which is much larger in this 

 ms allied to it. It is a sort of crop 



or proventricnlus (the organ of Delle Chiaje), and rarely oc- 

 curs iu the GnstroiKxls. On laying it open, it may be seen 

 to be -ior end, and posteriorly divided by 



rtitions into small cavities. The 

 iKjyond ii again slender, and leads to the 

 apex of the shell, partly embedded 



in the livtjr-mass wlii'-'i lies mainly beyond it. From 

 the stomach the ; returns to the head, widely dilat- 



ing into a larp laud cloaca, before the free up- 



! vent, wi: .uited on the right side behind and 



o right tentacle. The nervous system is 

 f large ganglia, forming the brain 

 ganglia) situated just below and behind 

 other ganglia were not traced, but as 

 >r<i there are three pairs of ganglia, 

 phageal ganglia) with commissures 

 t to the pedal or infraoesophageal 



ganglia, tli n tie O3sophageal nervous ring, while the 



1 or parieto nic ganglia are placed at a varying 



distance behind the head. 



The heart, contained in its pericardial sac, and consisting of 

 a ventricle and auricle, is situated near the posterior end of 

 the gills. The latter are disclosed by laying aside the man- 



