888 ME. WALTEE E, COLLINGE OK THE SEXSOET [DeC. 17, 



the trigeminal facial and vagus. It may conveniently be expressed 

 as follows : — 



TRIGEMINAL. 



Ramus ophthalmicus siiperficialis. ( Innervate the main canal of the head 

 Bamus ophrhalviicus ^ofimdus. \ and the supra-orbital branch. 

 Bamus huccalis. \ ^""^'"IJ^^ ^\ sub-orbital branch and 



Bamus maxillaris superior. ^he Y-shaped commissure of the mam 



[ canal oi the head. 



Bamus maxillaris inferior Innervates the maxillary division of 



the maxillo-niandibular branch. 



Bamus mandibularis Innervates the mandibular division of 



the maxillo-mandibular branch. 

 FACIAL. 



Bamus hyoideus Innervates the jugular canal of Garman. 



VAGUS. 



Bam us 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 I 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 Proio- 

 jpterus. 



6. There is a commissural connection between the vagus and 

 facial (■? trigeminal), probably homologous with that which obtains 

 in Cerntodus, 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 ampuUary 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, how- 

 ever, have preferred to regard them as a distinct class. The 

 results obtained by an examination of the innervation of the 

 sensory canal-system strengthen, I think, the grounds for this 

 separation. 



VI. BiBLIOGEAPHT. 



1. AxLis, 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, Feauz. — " Die Lorenzinischen Ampullen der Sela- 



chier." Arch. f. mikr. Anat. 1868, vol. iv. pp. 375-391, 

 pi. xxiii. 



3. CoLLiKGE, Waltee E. — " The Sensory Canal-System of 



Eishes. Pt. I. Ganoidei." Quart. Joum. Micros. Sci. 



1894, vol. xxxvi. pp. 499-537, pis. 39, 40. 



4. CoLLLNGE, Waltee E. — " On the Unsymmetrical Distri- 

 bution of the Cranial Kerves of Pishes." Jotirn. Anat. 



1895, vol. xxix. pp. 352-4. 



