COMPARED WITH THAT OF NAUTILUS POxMPILIUS. 
287 
The funnel lobe, shell-muscles, and the principal artery run- 
ning upon the oesophagus, giving it a small vessel and termi- 
nating in fine branches, which pass through the nervous ring 
towards the buccal mass, need no references. 
Fig. 2. The auditory sac : natural size. 
Fig. 3. The otokonia : highly magnified. 
Fig. 4 exhibits the opening of the tongue-sac a, the lingual papillae h, and those distri- 
buted upon the buccal folds of lining membrane c. 
d. Semi-cartilaginous substance forming the matrix of the horny 
jaws, and affording attachment to muscles f. 
e. Opening of the oesophagus. 
g. Sublingual processes, the inferior one being detached from the 
corresponding jaw. 
Immediately in front of the lingual papillae, the mucous membrane 
forms two small wing-like folds, lying side by side, h, which serve 
to close the opening of the lingual sac ; and a linear projection 
extends, from between them, along the roof of the sac, being 
impressed by the teeth of the rachis, and the internal series of 
uncini on either side. The microscopic structure of the sup- 
porting cartilage of the lingual strap is perfectly similar to that 
of N. Pomj)ilms\ and with the trifling difference, that the uncini 
of N. umhilicatus are a little shorter than those in N. Pompilius, 
the lingual ribbon, and I may also include the horny jaws of both, 
so nearly resemble one another as to render separate illustration 
quite unnecessary. 
Fig. 5. A cluster of papillae enlarged to show their general form and character. 
Fig. 6. Tip of one of the papillae, highly magnified to show the investing columnar 
epithelium. A considerable number of these almost filiform cells have been 
removed in order to display the rest more satisfactorily. 
Fig. 7. Several of the renal follicles detached, with a portion of branchial vessel with 
which they were connected : natural size. 
Fig. 8. Enlarged representation of the follicles seen at fig. 7, showing the funnel- 
shaped membranous processes appended to their free extremity, and the 
openings by which they communicate with the cavity of the branchial 
vessel. 
Fig. 9. Crystalline bodies often occurring within the follicles. 
Fig. 10. A few of the fibres which occasionally present themselves, disposed in flat- 
tened and branched bundles, between the external and internal coats of 
the follicles. 
The remaining figures represent highly magnified portions of the lining 
membrane. 
