20 



CLASS I.— CEPHALOPODA. 



Body enclosed in a sac formed by the mantle ; head 

 distinct, furnished with all the organs of sense, and sur- 

 rounded with fleshy filaments, which act as organs of 

 prehension and locomotion. 



CephaUjjhora, Blainville. Antlio-brachiophora, Gray. 

 CephaUpoda, Cuvier. Kecj^aXri, head ; 7r68a, feet : feet 

 attached to the head. 



Body enveloped in the mantle, which forms a muscular 

 sac or bag, open anteriorly. Head distinct, protruded 

 from the sac. Mouth situated anteriorly, armed with a 

 pair of horny or calcareous mandibles, resembling the 

 bill of a bu'd, and placed at the bottom of a cavity 

 formed by the base of the fleshy appendages ; tongue 

 covered with horny points ; oesophagus dilated into a 

 kind of crop ; stomach a muscular gizzard, succeeded by 

 a membranous, somewhat spiral sac ; intestine termi- 

 nating near the neck. Liver large, discharging the bile 

 into the membranous stomach. Circulatory appara- 

 tus, a systemic heart and an arterial system, and in 

 many, two pulmonic hearts. Branchise equal, symme- 

 trical, communicating externally by an infundibulum, 

 into which the rectum also opens. Generative system 

 of distinct sexual organs : there being in the male a 

 testis, vas deferens, and fleshy penis — the latter situated 

 on the left side of the vent ; in the female, an ovary si- 

 tuated in the bottom of the mantle-sac, and two ovi- 

 ducts. The head terminated by a circle of elongated 

 fleshy organs, generally furnished with acetabula, or 



