MUSTKLUS Lx^VIS. 229 



exact inter-homologies cannot as yet be definitely affirmed, 

 certain very probable homologies can certainly be arrived at. 



The portio ophthalmici profundi of bony ganoids, and the 

 ramus ophthalmicus profundus and ramus ophthalmicus 

 superficialis trigemini of elasmobranchs, are general sensory 

 cutaneous nerves, and probably contain all of those general 

 sensory elements that belong to the ophthalmic nerves of 

 vertebrates. 



The portio ophtlialmici profundi of ganoids is the homo- 

 logue either of the ramus ophthalmicus superficialis trigemini 

 of elasmobranchs, or of a frontal branch of the ramus pro- 

 fundus that has, in certain selachians (Lfemargus), the posi- 

 tion of a superficial ophthalmic nerve ; or it is the horaologue 

 of both those nerves of elasmobranchs. In the higher 

 animals this portio profundi becomes the frontal branch of 

 the ophthalmic nerve. 



The ramus ophthalmicus profundus of elasmobranchs ;ind 

 of Polypterus, and that nerve alone, is the homologue of the 

 ramus nasalis or naso-ciliaris of higher animals. This nerve 

 and the portio ophthalmici profundi vary inversely in im- 

 portance. 



The ramus ophthalmicus superficialis trigemini of Amia is 

 a communis nerve, and is probably the homologue of that 

 part of the ophthalmicus superficialis facialis of Acipenser 

 and elasmobranchs that is derived from the so-called dorsal 

 root of Trigeminus II. This latter root arises from the lobus 

 trigemini of the latter fishes, is considered by certain authors 

 as a lateral sensory root, and is called by them the dorsal 

 root of the ramus opthalmicus superficialis facialis. 



'^riio ramus ophthalmicus superficialis facialis of Amia is a 

 lateral sensory nerve, and has its probable homologue in that 

 part only of the ophthalmicus superficialis facialis of Acipenser 

 and elasmobranchs that is derived from the so-called ventral 

 root of Trigeminus II. This root arises, in all fishes, from the 

 tuberculum acusticum. 



The so-called ramus ophthalmicus superficialis trigemini of 

 teleosts is the ramus ophthalmicus superficialis trigeinini of 



