61 



i. The united internal portions of the pillars of the funnel. 

 k. k. The shell-muscles. 



I. I. Their terminations, or surfaces of attachment, 

 m. The transverse fibres which connect them. 



PLATE IV. 



Nautilus Pompilius, in the prone position, with the labial processes and ten- 

 tacles, the mandibles, and the digestive organs displayed. 



a. a. The hood, or upper part of the oral sheath longitudinally divided. 



b. b. The posterior lobes or angles of the hood. 



c. c. The posterior concavity of the hood. 



d. d. The ridge in the same. 



e. e. The cut-surfaces of the above parts. 



/./. The internal surface of the oral sheath. 



g. g. The external labial processes. 



h. h. The external labial tentacles. 



i. i. The internal labial processes. 



k. k. The internal labial tentacles. 



I. The olfactory laminae. 



m.m. The circular fringed lip, longitudinally divided. 



n. The superior mandible. 



0. The inferior mandible. 



p. The muscular basis on which the mandibles are fixed. 



q. q. Tlie superior pair of muscles which retract the jaws. 



r. r. Tlie semicircular muscle which protrudes the jaws, divided longitudinally. 



s. The oesophagus. 



t. The crop. 



M. The narrow canal leading to 



V. The gizzard. 



w. The intestine. 



w. The terminal fold of intestine drawn out of its situation. 



X. The anus. 



y. The laminated pancreatic bag. 



