ZOOLOGY 



s K< -r. 



is a series of bilaterally arranged lobes which represent the fore- 

 foot or the epipodia of other Molluscs. These are beset with 

 numerous slender, three-sided 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 a number of annular constric- 

 tions, which give the tentacle a transversely ridged character. 



Jaws in/ 



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FIG. 684. Nautilus pompilius, diagrammatic lateral view of a female specimen, enclosed 

 in its shell, cart, cartilage ; cten. ctenidia ; hd. hood ; inf. funnel ; jaivs, jaws ; mant. mantle ; 

 mant'. dorsal mantle fold overlapping the coil of the shell ; mus. position of lateral mass of 

 muscle : nid. nidamental glands ; sept, first septum ; siph. siphuncle. (After Keferstein.) 



There are no suckers : but the ridged surfaces enable the tentacle 

 to adhere firmly to rough objects. The tentacles are arranged in 

 two series, an outer and an inner. The outer, which are borne on 

 an annular muscular ridge of the foot, are nineteen on each 

 side in both sexes. Anteriorly this muscular ridge is thickened to 

 form a massive lobe the hood (Figs. 684, 685, hd.) in which 

 there is a concavity for the reception of the coil of the shell. The 

 hood bears two tentacles, and has the appearance of being com- 

 posed of the immensely developed sheaths of these, completely 



