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IOWA ACADEMY OF SCIENCE 
dorsal to the mandible into three branches. One of these passes straight ven- 
trally through the mandible between Meckel’s cartilage and the dentary bone 
to be distributed to the intermandibular (m. mylohyoideus anterior) muscles 
anterior and posterior, and to the skin of -the ventral surface of the head ex- 
ternal to these muscles. The distribution of this branch is that which usually 
obtains in the Urodela. Miss Bowers (1900) designates it in Spelerpes as md. 
interims V. A second branch runs anteriorly at the lateral border of the 
mandible supplying the skin of the side of the lower jaw. This branch also 
has nothing unusual in its distribution. It has been described in Amblystoma 
(Coghill, 1902), Spelerpes (Bowers) and Amphiuma (Norris, 1908) and evidently 
is a constant feature in urodele anatomy. Miss Bowers terms it r. md. ex- 
ternus V. The third branch runs anteriorly along the dorsal border of Meckel’s 
cartilage, then gradually shifts medially and ventrally between the cartilage 
and the angulo-splenial bone and fuses with a branch of the r. alveolaris VII. 
This combined nerve of general cutaneous and communis fibers runs anteriorly, 
presumably to supply the teeth and lateral floor of the mouth. This third 
branch has no peculiarities, and its anastomosis with the alveolaris has been 
described in Amblystoma and Amphiuma. Miss Bowers does not describe it 
in Spelerpes, but my own preparations of Spelerpes show it very distinctly, 
and that the anastomosis with the alveolaris undoubtedly occurs. None of these 
three branches of the r. mandibularis remain in the upper jaw, nor can I find 
any branches such as Dodds describes in the upper jaw. 
Coghill describes in Amblystoma an anastomosis between the motor portion 
of the r. mand. supplying the intermandibular muscles and the motor part of 
the r. jugularis VII supplying the interhyoid muscle. A similar anastomosis 
occurs in Plethodon. 
Of the ramus ophthalmicus profundus V Dodds says: ‘Tt soon divides into 
two branches. One of these extends dorso-lateral and breaks up in the muscles 
in front of the eye.” Although this is not a positive statement that this dorsal 
branch is motor, yet such an inference may be drawn. There are no muscles 
in Plethodon anterior to the eyeball unless we except the superior and inferior 
oblique muscles of the eyeball itself. Furthermore, this dorsal branch is ex- 
clusively general cutaneous in composition and is distributed to the upper eye- 
lid and the skin of the dorsal side of the head mesial and anterior to the eye. 
Examination of the published figures of the cranial nerves of Amblystoma, 
Spelerpes and Amphiuma shows that similar branches are found in these forms. 
Dodds correctly describes the three terminal divisions of the main portion of 
the r. oph. prof,: a mesial, a lateral and a ventral branch, the latter anastomos- 
ing with the r. palatinus VII. The condition seems to be similar to that in 
Amblystoma and Spelerpes. Of the exact nature of the anastomosis with the 
R. pal. VII the material studied does not give exact information. Apparently 
it differs from that described in Amblystoma and Amphiuma. 
In the material studied the lateral line system had disappeared. Hence the 
VII-VIII complex is much simplified over that of the larval stage. The VII-VIII 
nerves arise from the brain by three groups of rootlets: a dorsal communis, a 
middle auditory and a ventral motor group. From the common ganglion of the 
VII-VIII nerves an anterior auditory vestibular branch passes to the utriculus 
and the anterior and horizontal semicircular canals of the ear. From the posterior 
part of the ganglion a number of auditory branches pass to the sacculus, lagena, 
etc. Dodds says that a single small twig supplies this portion of the ear. From 
