xn PHYLUM MOLLrSCA 707 



conical hcad,^ bearing eyes and a system of tentacles, :md a 

 rounded sac-like truvk. Both head and trunk are very Alight Iv 

 compressed, the direction of the coni}iiv.ssi () n being, as in Sepia, 

 from the antero-dorsal towards the postero-ventral side, ;ml 

 are almost completely bilaterally symmetrical, <>nlv a very 

 slight disturbance of the symmetry being di-.-rniible. The 

 mouth, situated at the free extremity, is provided with a pair of 



cart 



mant 



cterv 



sejbt 



siph, 



FIG. lias. Nautilus pompilius, diagrammatic lateral view of a female specimen 

 in its shell, cart, cartilage ; cti.it. ctenidia ; hit. hood ; iitj, funnel; jaws, jaws ; numfc i 

 niiiiit'. dorsal mantle fold overlapping the coil of the shull ; mug. positiun nf lateral mass "f 

 uuiscle ; ,ii,i. nidamental glands ; s^it. first septum ; siph. .siplmiiclo. (After Kefurstein.) 



relatively enormous, partly calcified jaws (Fig. 638). Surrounding 

 the mouth is a series of bilaterally arranged lobes which represent 

 the fore-foot of other Molluscs. These are beset with numerous 

 slender tentacles, each provided with an elongated tubular sheath, 

 in the interior of which the greater part of the tentacle in the 

 retracted condition lies enclosed, only a small portion protruding. 

 Minute ring-like markings on the tentacle are due to the 

 presence of circular bands of muscular fibres. There are no 



