CRANIAL NERVES OF SIREN LACERTINA 279 
which have a similar distribution to that of the ramulus ophthal- 
micus profundus minor. From one is given off the superior 
ciliary nerve; with another the trochlearis nerve comes into close 
association. In Salamandra (von Plessen and Rabinovicz), 
Plethodon (Dodds, Norris) and Necturus (Norris and Buckley) 
a ramulus ophthalmicus profundus minor evidently occurs, very 
similar to that in Siren. In Amphiuma this branch is included 
in the ramulus nasalis internus V, or is very closely connected with 
the latter through anastomoses. Dorsally the ramulus nasalis 
internus of Amphiuma anastomoses with the ramus ophthalmicus 
superficialis VII and has the same general distribution as the 
ramulus ophthalmicus profundus minor of Siren and others; 
ventrally it enters the nasal capsule and has the same relations 
as the median terminal division of the ramus ophthalmicus pro- 
fundus V, ramulus nasalis internus proper, of Urodela in general. 
In Siren the anastomoses between the ramulus ophthalmicus pro- 
fundus minor and ramus ophthalmicus superficialis VII are insig- 
nificant and confined to a few small twigs. 
The main profundus nerve now passes, after giving off the 
ramulus ophthalmicus profundus minor, somewhat more laterally 
through the temporal muscle with the optic nerve on its ventro- 
medial border. Anterior to the entrance of the optic nerve into 
the eyeball the ramus ophthalmicus profundus lies between the 
temporal muscle and the eyeball (fig. 9). While passing the eye- 
ball the main nerve divides into the three terminal branches that 
seem to be characteristic of the Urodela (figs. 7, 8): (a) A large 
dorsal division (op.2), ramulus nasalis internus (not the 
r. nas. int. of Wilder), passes anteriorly into the nasal capsule, 
running along its medial dorsal border and over the olfactory 
nerve (fig. 6). Near the level of the anterior end of the brain 
it gives off a small branch (op.2a) which passes medially to take 
a position close to the middle line with its fellow of the opposite 
side, between the two frontal bones (fig. 5), farther anteriorly, 
dorsal to the anterior ends of the frontals (figs 3, 4), and is finally 
distributed to the skin of the extreme antero-dorsal part of the 
snout. In Amphiuma a small nerve with a similar distribution 
leaves the nasalis internus just before the latter enters the nasal 
