66 



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



2. 2. The anterior suboesophageal mass, or Pes anserinus, giving off (5. 5.) the 



nerves to the arms. 



3. 3. The great reniform or ophthalmic ganglions. 



4. 4. The posterior suboesophageal mass, giving off (6. 6.) the nerves to the 



cloak; and (8.) the nerves to the viscera. 

 7. 7. The ganglion stellatum. 

 9. 9. Two small spherical bodies attached to the pedicles of the ophthalmic 



ganghons. 



PLATE VIII. 



Various parts of Nautilus Pompilius. 



Fig. 1 . Plan of the cartilaginous skeleton. 



a. Tlie body of the skeleton, containing the venous sinus, the extent of 

 which is indicated by the dotted Une. 



b. b. The cephalic processes. 



c. c. The groove which lodges the anterior nervous collar, and ophthalmic 



ganglions. 



d. d. The infundibular processes. 



Fig. 2. The mandibles. 



a. The calcareous extremity of the upper mandible. 



b. The extended internal horny lamina of the same. 



c. The notched calcareous extremity of the lower mandible. 

 d. d. The extended external horny lamina of the same. 



Fig. 3. The upper mandible, showing the form of the calcareous extremity, 

 and the proportions of the external and internal horny laminse. 



Fig. 4. One half of the lower mandible, showing the different proportions of 

 the two horny laminee, and the extension of the horny substance at a, upon 

 which the calcareous matter is deposited. 

 a . The internal horny lamina. 

 b. The external horny lamina. 



Fig. 5. The mandibles and their muscles. 

 a. The upper mandible. 



