IOWA ACADEMY OF SCIENCE 
275 
The first lateral line branch given off from the trunk of the 
seventh nerve is the ramus mentalis externus VII. At the point 
where this branch leaves the main trunk there arises either from 
the main trunk or from the lateral line ramus a small branch that 
divides into two or three divisions that supply the post-orbital and 
jugular series of neuromasts. It will be seen that this small branch 
with its -divisions extends over a considerable territory. Dorsally 
it encroaches upon the occipital region so that a number of neuro- 
masts included by Kingsbury in the dorsal series of the trunk are 
supplied by it. The R. mentalis externus VII supplies the oral 
and angular groups of neuromasts. Some distance posterior to 
the emergence of the R. mentalis externus VII another large lateral 
line ramus leaves the trunk of the seventh nerve to supply the gular 
series of neuromasts. This ramus is termed by Kingsley 6 
as the R. hyomandibularis accessorius, and by Druner 7 as 
the R. cutaneus mandibulae medialis. This is evidently, as 
Druner recognizes, the ramus that in most Urodela arises with the 
R. mentalis externus in a common trunk from the seventh nerve. 
It is designated here as the R. mentalis internus VII, following the 
example of Coghill. Like the R. mentalis externus it consists solely 
of lateralis fibers. 
Three or four neuromasts of the extreme posterior portion of the 
jugular series have a somewhat peculiar innervation. From the R. 
jugularis VII as it enters the kerato-mandibularis division of the de- 
pressor mandibulae muscle there are given off two small twigs that 
pass laterally and posteriorly out through the muscle and emerg- 
ing subcutaneously, go one to the most dorsal of the neuromasts 
mentioned, while the second twig divides into three parts, one of 
these divisions supplying a second of these neuromasts, another di- 
vision the third neuromast in part, and the third division joining a 
nerve that connects with that peculiar branch of the seventh nerve, 
designated by Druner as the N. lateralis VII. This latter nerve de- 
serves a more extended mention. It was first described by Fischer 8 
as a structure peculiar to Amphiuma and said to be traced to the 
hyotrachealis (interbranchialis IV) muscle. Kingsley believed that 
6. Kingsley, J. S. The Cranial Nerves of Amphiuma. Tnfts College Studies, No. 7, 
1902. 
7. Druner, L. Studien zur Anatomie der Zungenbein-, Kiemenhogen- und Kehlkopf- 
musculatur der Urodelen, II Theil. Zool. Jahrb. , Abt. , f . Anat. u. Ontog. d. Thiere, Bd. 
XIX, Hft. 3 u. 4, 1902. 
8. Fischer, J. G. Anatomische Abhandlungen uber die Perennibranchiaten und 
Derotremen. Hamburg, 1864. 
