598 ALLIS. [VoL. XII. 
b. Ramus Ophthalmicus Superficialis Trigemini and Ramus 
Ophthalmicus Superficialis Facialis. 
The ophthalmicus superficialis trigemini (of¢ in many figures) 
arises in the adult, as in larvae, from the median and upper 
portion of the trigemino-facial ganglion immediately under the 
ophthalmicus facialis (off). It leaves the upper, lateral cham- 
ber of the eye-muscle canal and issues from the cranium with 
the ophthalmicus facialis by the ophthalmic foramen through 
the alisphenoid (offr, Figs. 9 and 10, Pl. X XI), immediately 
above the large trigeminal foramen. The two ophthalmic 
nerves are, from the very beginning of their extra-cranial 
course, closely and intimately associated. They run upward 
and forward along the side of the cranium, and not at some 
distance from it, as Schneider states, lying at first under the 
overhanging, cartilaginous roof of the orbit, and then under the 
overhanging frontal, which, opposite the eye, where the roof 
of the cnondrocranium is relatively narrow, projects so much 
beyond that roof that the nerves lie approximately under the 
middle line of the bone, and hence under that part of the supra- 
orbital sensory canal that lies in that bone. 
About opposite the front edge of the eye, the two ophthalmic 
nerves leave the orbit, and reach the upper surface of the chon- 
drocranium, passing as they do so through a notch in the edge 
of the cartilaginous cranium. This notch (z, Figs. 8, 9, and 
10, Pl. X XI) lies a little behind the prefrontal ossification, and 
a little in front of the middle point of the frontal bone, and is 
the preorbital incisure of Pristiurus, Prionodon, and Zygaena 
(No. 44, p. 71). It marks, as in those fishes, the posterior limit 
of the preorbital process (fv). The anterior limit of the proc- 
ess 1s defined, as in those fishes, by an ethmoid incisure (ze). 
Having reached the upper surface of the cranium, the ophthal- 
mic nerves continue directly forward, soon entering a groove on 
the under side of the frontal bone, in which they pass above the 
projecting hind end of the premaxillary. Leaving the groove 
at the front end of the frontal, they pass through the narrow 
strip of dermal, or subdermal, tissue that lies between that 
bone and the nasal, and then pass under the nasal, lying, in 
