300 EXPLANATION OF THE PLATES. 



62. Digestive organs, etc., of Nautilus Pompilius. (After 

 Owen, Memoir on Pearly Nautilus, t. 4.) a, The hood 

 or .upper part of the oral sheath longitudinall}^ divided. 

 6, Posterior lobes or angles of the hood, c, Posterior 

 concavity of the hood, d^ The ridge in the same, e, 

 The cut-surface of the above parts. /, Internal sur- 

 face of the oral sheath, gr, External labial processes, 

 /i, External labial tentacles, i, Internal labial pro- 

 cesses. /<?, Internal labial tentacles. I, Olfactory 

 laminae, m. The circular fringed lip, longitudinally 

 divided, n, Superior mandible o. Inferior mandible, 

 p. Muscular attachment of mandibles. 5, The superior 

 pair of muscles which retract the jaw^s. r. The semi- 

 circular muscle which protrudes the jaws, divided 

 longitudinally, s, The oesophagus. ^, The crop, u, 

 The narrow canal leading to u. The gizzard, uj. The 

 intestine, to', The terminal fold of intestine drawn 

 out of its situation, x, The anus, r/. The laminated 

 pancreatic bag. z. The liver. 15, A branch of the 

 anterior aorta, which ramifies in the membrane con- 

 necting the two portions of the terminal fold of the 

 intestine. 19. Continuation of the posterior aorta 

 along the dorsal aspect of the crop. 20. Its bifurca- 

 tion at the oesophagus, to form a vascular circle cor- 

 responding to the nervous circle round that tube. 21, 

 22, Arteries, of the crop, gizzard, etc. . . 63, 65 



63. Nautilus Pompilius, in its shell, the latter a section to 



show the interior, a. The mantle. 6, Its dorsal fold. 

 e, Nidamental gland. (7, Shell muscle, i i z, Siphon, 

 fc, Funnel. 7i, Hood, o o 0, Exterior digitations. p, 

 Tentacles. 8, Eye. ^;, ^, Septa, z. Last chamber, 33,37 



Plate 5. 



64. Triton variegatum, Brug. pr^ proboscis ; 0', oral mass ; 



oc^ eye ; ;S', respiratory siphon ; 6r, branchi^ ; c, heart 

 /?,, liver ; ^, testicle; (7, cerebral ganglion* y', pedal 

 ganglion ; g" , visceral ganglion ; i, intestine ; v d, vas 

 deferens; a, anus ; p, penis. . . . . .11 



65. Nervous system of Ommastrephes todarus. Ventral 



face (Hancock), gv^ Visceral ganglion. p. Optic * 

 nerve, g p. Pedal ganglion, ghs, ghi, Superior and 

 inferior buccal ganglia. 6, Arm nerves, n v, Visceral 

 nerves, g s t, Granglion stellatum. n p i, Fin nerves, 

 n ce, (Esophageal nerves, g v e, Splanchnic ganglion, 

 g X, Granglion on the vena cava, g h r^ Branchial 

 ganglion, b r, Branchial nerves, n y, Nerves of the 

 ink-bag' and rectum. . . . . . . .10 



