MOLLUSCA. CEPHALOPODA. 169 



foot extends round the mouth, and its margin is produced 

 into eight or ten (many in Nautilus) processes or arms 

 (fig. 48 e,f), which are provided either with sucking discs 

 or tentacles, and are used in prehension and locomotion. 

 The mid-foot is in the form of a tube termed the funnel 

 (d) which opens in front to the exterior, and behind into 



FIG. 48. Diagram of a vertical median antero-posterior section of Sepia 

 qfficinalis. a, shell; b, mouth of mantle-cavity; c, mantle-cavity; 

 d, funnel ; e, lobes (arms) of the fore-foot ; /, long arm of the fore- 

 foot ; g, the upper beak or jaw ; h, the lower beak or jaw ; i, odonto- 

 phore; k, the viscero-pericardial sac; I, the nerve-collar; m, the 

 crop ; n, the gizzard ; o, the anus ; p, left gill ; q, ventricle of the 

 heart; r, renal glandular mass; s, left nephridial aperture; t, viscero- 

 pericardial aperture ; u, branchial heart ; w, ink-sac. (After Lan- 

 kester, Zool. Art. Encyc. Britt.) 



the mantle-cavity (c). The funnel may be either a perfect 

 tube or may be formed by the apposition of two troughs. 

 The hind- foot is absent. On the upper surface of the 

 head there are two large eyes, which, except in Nautilus, 

 are almost as highly developed as in vertebrate animals. 

 The mantle is formed by a single fold of the integument, 

 which passes quite round the body of the animal; but 

 dorsally the fold is very shallow so that the mantle- cavity 

 exists mainly on the ventral surface. The gills (p) are placed 



