ORGANS OF DIGESTION. 375 



filaments, is covered with sensitive and retractile lips which 

 move by distinct levator and sphincter muscles. The mus- 

 cular bulb of the mouth contains, in the naked species, 

 two strong, curved, sharp, "horny mandibles, like those of 

 many oviparous vertebrata; but in the nautilus (Fig. 122. B. a.) 

 the jaws are calcified and possess broad and dentated mar- 

 gins. The lower mandible extends beyond and curves over 

 the point of the upper, and both are hollow behind and 

 expanded at their base, like the vaginiform horny mandibles 

 of many vertebrata. The mandibles here move vertically 

 as in all the higher classes, not transversely as in articulata. 

 The short muscular tongue is covered with regular rows 

 of sharp horny recurved spines as in many molluscous and 

 vertebrated animals, attached to a cartilaginous base, and 

 the back part of the mouth receives the secretions generally 

 of an upper smaller pair and an inferior larger pair of salivary 

 glands, the component tubuli of which have already assumed 

 the conglomerate form and lobulated character of these or- 

 gans in higher classes. The inferior or large pair of salivary 

 glands are situate at the upper and back part of the liver, 

 and their two ducts early unite to ascend to the mouth 

 as one median canal. 



The oesophagus of the cephalopods passes through the 

 cranial cartilage, and continues for a short distance narrow 

 and equal, behind the upper end of the elongated liver, then 

 dilates into a crop, which sometimes forms a short cir- 

 cumscribed membranous cavity, and in others a simple elon- 

 gated dilatation, as we see the forms of that organ to vary in 

 the class of birds, and it is generally marked with longitudinal 

 plicee of its internal mucous coat (122. B. b. c.) Below this 

 dilatable first cavity the oesophagus continues downwards 

 narrow, and to the right side of the dorsal part of the cavity 

 of the trunk, where it enters the second stomach or muscular 

 gizzard. The crop forms a short circumscribed cavity, and 

 is high in its position, in the octopus-, it is lower and more elon- 

 gated in the nautilus (122. B.C.) more narrow in the loligopsis 

 (122. D. .), and scarcely forms a perceptible dilatation in 

 the loligo and the sepiola (122. C. a.) The muscular gizzard, 

 situate on the right side below the middle of the abdominal 

 cavity, varies also in its form, muscularity, and relative size, 

 and is provided with a thick, tough, coriaceous internal lining 



