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Show 888 MR. WALTER E. COLLINGE ON THE SENSORY [Dec. 17, the trigeminal facial and vagus. It may conveniently be expressed as follows:- TRIGEMINAL. Ramus ophthalmicus superficialis. f Innervate the main canal of tbe head Ramus ophthalmicus profundus. \ and the supra-orbital branch. Ramus buccalis. \ Enervate tbe„ s u b - ° r b i t a l b ™ ? c h a ? d Ramus maxillaris superior. the Y-shaped commissure of the main [ canal ot the bead. Ramus maxillaris inferior Innervates the maxillary division of the maxillo-mandibular branch. Ramus mandibularis Innervates the mandibular division of the maxillo-mandibular branch. FACIAL. Ramus hyoideus Innervates the j ugular canal of Garman. VAGUS. Ramus vagi lateralis Innervates th e lateral canal. It will thus be seen that the facial nerve is almost entirely replaced by the trigeminal, not unlike the condition 1 have previously described in the Physostomous Teleostei (5). 5. The vagus arises distinct from the glossopharyngeal nerve, and leaves the skull by a separate foramen. The branching is not unlike that figured and described by Pinkus (13) in Protopterus. 6. There is a commissural connection between the vagus and facial (? trigeminal), probably homologous with that which obtains in Ceratodus, Protopterus, and Lepidosiren. 7. The combined vagi lateralis and commissure run posteriorly quite close to the vertebral column, as in Lepidosiren. 8. In the form of the canals and branches, and the possession of ampullary canals, the system resembles that found in the Elasmobranchii; on the other hand, in the innervation it more nearly resembles the condition found in the Teleostei and Dipnoi. 9. Hitherto most zoologists have classed the Holocephali with the Elasmobranchii; Huxley, Gegenbaur, and a few others, however, have preferred to regard them as a distinct class. The results obtained by an examination of the innervation of the sensorv canal-system strengthen, I think, the grounds for this separation. VI. BIBLIOGRAPHY. 1. ALLIS, E. P.-"The Anatomy and Development of the Lateral Line System in Amia calva." Journ. Morphology, 1889, vol. ii. pp. 463-569, pis. xxx.-xlii. 2. BOLL, FRANZ.-'• Die Lorenzinischen Ampullen der Sela-chier." Arch. f. mikr. Anat. 1868, vol. iv. pp. 375-391, pi. xxiii. 3. COLLINGE, W A L T E R E.-" The Sensory Canal-System of Fishes. Pt. I. Ganoidei." Quart. Journ. Micros. Sci. 1894, vol. xxxvi. pp. 499-537, pis. 39,40. 4. COLLINGE, W A L T E R E.-" On the Unsymmetrical Distribution of the Cranial Nerves of Fishes." Journ. Anat, 1895, vol. xxix. pp. 352-4. |
