REFERENCE TO PLATES. 295 



FIGURES. PAGE. 



k. The origin, on the left side, of the muscle which pro- 

 trudes the jaws. I. The inner concave surface of the great 

 shell-muscles. m. The termination of the right muscle. 

 n. Orifices by which the vena cava communicates with the ab- 

 dominal cavity, o. The eye laid open. p. The pedicle. 

 q. The pupil seen from within, r. The cut-edge of the sclerotic. 

 s. The retina, t. The dark pigment deposited on its anterior 

 surface, and lining the cavity of the globe. 1. The brain, or 

 central commissure. 2. Anterior sub-oesophageal ganglions. 

 3. Ophthalmic ganglions. 4. Posterior sub-oesophageal gan- 

 glions. 5. Nerves of the digital tentacles. 6. Nerves of the 

 external labial tentacles. 7. The nerves bringing the labial 

 ganglions into communication with the anterior sub-cesophageal 

 ganglions. 8. Internal labial ganglions. 9. Nerves of the in- 

 ternal labial tentacles. 10. Olfactory nerves. 11. Infundibular 

 nerves. 12. The origins of the lingual and maxillary nerves. 

 13. Nerves of the great shell-muscles. 14. Visceral nerves. 

 15. Branchial nerves. 16. Visceral ganglions. 17. Nerves 

 ramifying on the vena cava. 



2. The olfactory laminap, magnified and separated 35 



3. Brain of Cuttle-fish (Sepia officinalis, L.) 32 



1. The brain, corresponding to the central commissure of the 

 Nautilus. 2. The anterior sub-esopliageal mass, or Pes anser- 

 inus, giving off (5) the nerves to the arms. 3. The great reni- 

 form or ophthalmic ganglions . 4. The posterior sub-cesophageal 

 mass, giving off (6) the nerves to the cloak ; and (8) the 

 nerves to the viscera. 7. The ganglion stellatum. 9. Two 

 small spherical bodies attached to the pedicles of the ophthal- 

 mic ganglions. 



Plate 3. 



1. Anatomy of Nautilus Pompilius. From Owen, Memoir on 



Pearly Nautilus, pi. 2 25 



a. The mantle, b. Its dorsal fold collapsed, c. Its anterior 

 margin, d. The process of the mantle which separates the 

 funnel from the head. e. Convexities produced by the ovarian 

 gland. /. Orifice of the funnel a little widened ; the funnel 

 itself is drawn down to show the surface of the oval sheath 011 

 which it rests, g. The levatores infundibuli exposed by laying 

 open the canals in which they were concealed, h. The hood. 

 L Its superior plane surface longitudinally divided, k. The 

 cut surfaces. I. The smooth internal surface of the oval 

 Sheath, m. The digitations, showing their orifices, the tenta- 

 cles being retracted (the entire number is given on the right 

 side), m'. The large papillose digitation. n. The inferior 

 parietes of the oral sheath, o. The external labial processes. 

 p. The internal labial processes, q. The convex outer surface 

 of the organ of smell, r. The labial tentacles. . One of the 

 ophthalmic tentacles, t. The eye. u. The inferior ridge. 



2. An ophthalmic tentacle magnified, showing itslaminated structure. 



3. A digitation with its tentacle magnified. 



a. The free extremity of the digitation. a'. The cut-sur- 

 face separated from the parietes of the head. b. The digital 

 tentacle. b f . The cut-surface of the te'ntacle, exposing c. The 

 central nerve. 



