250 ALUS. [Vol. XVIII. 



frontal. There they fuse more or less completely to a single trunk, 

 and, running forward, immediately mesial to the strong ridge on 

 the ventral surface of the frontal, traverse the preorbital incisure, 

 and reach the dorsal surface of the cartilage of the antorbital 

 process. There the single trunk formed by the fusion of the two 

 nerves continues forward between the frontal bone and the antor- 

 bital cartilage, in a groove on the dorsal surface of the latter, and 

 then runs dorsal to the nasal sac toward the end of the snout. 

 In their course the two nerves lie dorsal to all the other nerves and 

 to all the muscles of the orbit. 



The ophthalmicus facialis always gives ofif three branches, and 

 sometimes four, before it fuses with the ophthalmicus trigeminus. 

 These branches pierce the frontal and enter the supraorbital lateral 

 canal, going to organs 7, 6, 5 and 4 of the line. The branch that 

 goes to organ 4 usually arises from the single trunk formed by the 

 fusion of the ophthalmic nerves. A fifth branch arises from the 

 fused nerves as they pass dorsal to the nasal sac. It separates 

 into two parts, each of which enters the nasal bone, one in- 

 nervating organ 3 and the other organ 2. No important 

 branches other than those described were given off by the two 

 nerves up to this point, but it is evident that there either must have 

 been numerous small branches, representing parts of the ophthal- 

 micus trigemini, or that fibers of that nerve must accompany the 

 lateral sensory branches that go to the several organs of the supra- 

 orbital canal. They could not however be traced, nor could the 

 branch that must innervate the anterior head line of pit organs. 



Distal to the branch to organ 2 supraorbital the ophthalmic trunk 

 continues forward, lying dorsal to the nasal sac and passing be- 

 tween the ligament that extends from the dorso-lateral process of 

 the ethmoid to the anterior end of the maxillary and the one that 

 extends from the nasal bone to the maxillary. The nerve thus has 

 the relations to these two ligaments that it has, in certain specimens 

 of Amia, to two heads of the fourth division of the levator max- 

 illae superioris muscle (No. 4, p. 608). The nerve, in Scomber, 

 here forms one or two anastomoses with the terminal portion of 

 the maxillaris superior trigemini, and is distributed, with the lat- 

 ter nerve, to the anterior end of the snout. It sends no branch to 

 organ No. i supraorbital, that organ being innervated, as already 



