No. 3.] MUSCLES AND NERVES IN AMIA CALVA. 573 
maxillae superioris, Csd1, and the spiracle muscle are all said by 
him to be innervated by a single branch of the r. maxillaris 
inferior trigemini, the branch being given off immediately after 
the main nerve issues from its foramen. The branch runs 
outward and backward under the postorbital process along 
the front or outer surface of the levator, and then apparently 
backward along the lateral surface of the levator and the outer 
surface of Csd:. In Mustelus (Tiesing) the corresponding 
muscles have a similar innervation, the nerve innervating them 
being sometimes double. 
In Galeus the larger spiracle muscle and the levator maxillae 
superioris are innervated by a branch of a small double nerve, 
which arises inside the cranial cavity, to all appearance from 
the upper surface of the truncus trigeminus, or of its ganglion. 
As it issues through the main trigeminal foramen this double 
nerve lies along the upper surface of the inferior maxillary 
nerve, crossing that nerve from its inner to its outer edge. 
It then turns under the nerve, to its lower surface, and con- 
tinues forward in this position to the upper edge of the upper 
jaw. Here, as the inferior maxillary turns downward and back- 
ward, the double nerve issues from beneath it, at its inner edge, 
and, running forward, supplies the muscle Add8. The nerve 
is so closely applied to the inferior maxillary, and, where it 
issues from beneath it, appears so exactly like a branch of that 
nerve, that it would not have been recognized as a separate 
nerve if the arrangement of the nerves and muscles in Amia had 
not indicated that it must be there as such. It is unquestion- 
ably the r. ad musc. levator maxillae superioris of Amia, but the 
nerve in Galeus is always double, as it was found to be in one 
specimen only of Amia. From the outer strand of the nerve 
in Galeus, soon after it leaves the cranium, a branch is sent to 
the levator maxillae superioris and the larger spiracle muscle, 
which two muscles therefore unquestionably correspond respec- 
tively to the second and first divisions of the levator maxillae 
superioris in Amia. The same strand then innervates the 
lower and interior portions of Add, which accordingly corre- 
spond to the third division of the levator in Amia, while the 
orbital part of the muscle, which is innervated entirely by the 
