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 ^mck- 

 ered swollen lips. Cutting down from between the tentacles, 

 a lai'ge buccal mass, the pharynx, is exposed. The mouth- 

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

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

 mouth lies tlje "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 (supracesophageal gan- 

 glion) ; just behind and beneath which are the two large 

 salivary glands. The oesophagus suddenly dilates into a 

 large stomach-like pouch, which is much larger in this 

 species than in other forms allied to it. It is a sort of crop 

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

 curs in the Gastropods. On laying it open, it may be seen 

 to be spong}' at its anterior end, and posteriorly divided by 

 numerous transverse partitions into small cavities. The 

 o?s(_iphagus beyond it is again slender, and leads to the 

 stomach situated in the apex of the shell, partly embedded 

 in the liver-mass which lies mainly heyond it. From 

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

 ing into a large sacculated cloaca, before the free up- 

 turned vent, which is situated on the right side behind and 

 to the right of the right tentacle. The nervous system is 

 represented by a pair of large ganglia, forming the brain 

 (siipraoesophageal ganglia) situated just below and behind 

 the phar}Tix. The two other ganglia were not traced, but as 

 a rule in all Ceplialoplwra there ai-e three pairs of ganglia, 

 i. c, the brain (supracesophageal ganglia) with commissures 

 passing around the gullet to the pedal or infraoesophageal 

 ganglia, thus forming the esophageal nervous ring, while the 

 visceral or parieto-splanchnic 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- 



