THE CRANIAL NERVES OF SIREN LACERTINA. 
BY II. W. NORRIS. 
Ill this preiimiuary account of the cranial nerves of Siren little ref- 
erence will be made to the characteristic urodele features, but the de- 
scriptions will deal chiefly with those characters that have a special 
significance in Siren. 
For our knowledge of the cranial nerves of Siren we are indebted to 
the researches of Fischer (1864), H. II. Wilder (1891) and Druener 
(1904). ’ 
The olfactory neiwe in Siren is double. A posterior series of rootlets 
gives rise to a trunk supplying the anterior nasal epithelium and Jacob- 
son’s organ; an anterior series of rootlets innervates the posterior nasal 
epithelium; the two series in origin and distribution are distinct, no 
observable anastomosing between the two olfactory trunks taking place. 
The optic and eye-muscle nerves are of the usual form found in uro- 
dele amphibians, all being imperfectly developed in consequence of the 
rudimentary condition of the eyes. 
■ Of the anaslomoses between the fifth and seventh nerves found in other 
Urodela the following occur in Siren : 1. General cutaneous fibers from 
the gasserian ganglion unite with the ramus ophthalmicus superficialis 
(lateral line) to form a supra-orbital trunk. 2. An infra-orbital trunk 
is formed by the union of general cutaneous fibers from the gasserian 
ganglion with the ramus buccalis VII (lateral line). A branch of the 
infra-orbital trunk, containing both lateral line and general cutaneous 
fillers, combines with a branch of the ramus ophthalmicus profundus V 
(general cutaneous fibers) to form a nm’ve that sends its lateral line 
fibers to innervate the anterior portion of the infra-orbital series of 
neuromasts and its general cutaneous component to form an anastomosis 
with the ramus palatinus VII. 3. The palatinus-ophthalmicus anasto- 
mosis at first sight seems to be peculiar, but is /found to fall into line with 
that described in Amblystoma (Coghill) and Amphiuma (Norris). 4. 
Tiie anastomosis between the alveolaris VII and a branch of the ramus 
mandibularis V, that seems to be characteristic of the Urodela, occurs 
in Siren to the extent only that the two branches in question pass a 
