THE SENSORY CANAL SYSTEM OF FISHES. 537 
orbital branches is not shown, in order to show the branching of the olfactory 
nerve. Z. C. The most anterior portion of the lateral canal, where it 
joins with the main canal of the head, MW. C.; in its course forwards it gives 
off the branches Oc. com., Hyom., S. or., and Sp. O. Hyom. The hyoman- 
dibular branch, innervated by the ramus opercularis superficialis No. 4, 
7.0.4. It divides into two smaller branches, viz. a mandibular, Mz., and a 
maxillary, Mz. §. or. The sub-orbital branch passing posterior to the orbit 
and meeting with the supra-orbital, Sp. o., in the region marked Sp. o%. In 
the region Sp. o'. short branches are given off. .§.,8. O!. The combined supra- 
and sub-orbital branches which give off in their anterior portion the branches 
S. 8. O?. and S. §. 0%.; 8.8. O*. indicates where the combined branches make 
an outward curve and join with their fellow of the opposite side. 
Lettering.—Hyom. Uyo-mandibular branch. 7. Lateral division of the 
vagus. J/'. Branch of lateralis vagi. JZ. C. Lateral canal of the trunk. M. 
Mouth. M. C, Main canal of the head. MM/z. Mandibular branch of the hyo- 
mandibular branch. Mz. Maxillary branch of the hyomandibular branch. J. 
Nares. Oc. com. Branches from the main canal in the occipital region. Or. 
Orbit. 7. 6. Ramus buccalis, with the branches a, 6, c, d, ande. 7. m. 
Ramus mandibularis, trigeminal. 7. m'. Ramus mandibularis, facial. 7. me. 
Ramus maxillaris. 7.0. Ramus opercularis superficialis, with the branches 
1, 2, 3, and 4. 7. 0. p. Ramus opthalmicus profundus. +r. o. s. Ramus 
opthalmicus superficialis. 7. o¢. Ramus oticus. 7. p. Ramus palatinus. 
S. or. Sub-orbital branch of the main canal. Sp. Spiracle. Sp. o. Supra- 
orbital branch of the main canal. §. 8. 0. The combined supra- and sub- 
orbital branch. Vg. Vagus. V. gi. Ganglion of vagus. 
Fic. 13.—Dorsal view of the head of Acipenser. ‘The sensory canal 
system is marked in red. Lettering as below. x 3. 
Fic. 14.—Lateral view of the same. x 2. 
Lettering.—d. eth. Dermo-ethmoid. d. ec. eth, Dermo-ect-ethmoid. d. oe. 
Dermo-occipital. ep. Epiotic. fr. Frontal. 2. C. Main canal of the head. 
oc. com. Occipital commissure. op. Operculum. or. Orbit. pa. Parietal 
pt. Post-temporal. §. 07. Sub-orbital branch. s. 0, Sub-orbital bones. Sp. O. 
Supra-orbital branch. Sz. Squamosal. 
