No. 3.] MUSCLES AND NERVES IN AMIA CALVA. 499 
determine from my sections whether it lay along the inner or 
the outer surface of the membrane. When it reaches a point 
slightly above and behind the optic nerve, it either perforates the 
membrane from its inner to its outer surface, or sends an impor- 
tant branch inward through the membrane, and then turns 
sharply outward and slightly downward above and behind the 
optic nerve, and, lying close to and behind the nerve, along its 
open edge, and at no place inside the nerve, as Goronowitsch 
(No. 50, p. 443) seems to have found in the adult, enters the 
eyeball with it. 
The external carotid (ec, Fig. 28, Pl. X XV) enters the upper, 
lateral chamber of the eye-muscle canal through the small 
external carotid foramen which lies in the petrosal immediately 
below and in front of the large facial foramen. In the eye- 
muscle canal it runs upward and forward under or in front of 
the trigemino-facial ganglion, and near the front end of that 
ganglion separates into two parts. One of these parts, the 
ophthalmic portion of the artery (ecof), issues from the canal and 
enters the orbit through the ophthalmic foramen with the 
ophthalmic branches of the facialis and trigeminus; the other 
or mandibular portion (ecm) issues through the trigeminal fora- 
men with the truncus trigeminus, which it accompanies. Imme- 
diately outside the cranium the mandibular portion gives off 
the afferent pseudobranchial artery (afs), which runs backward 
to the uppper surface of the pseudobranch. From the lower 
surface of the pseudobranch the efferent pseudobranchial artery 
(eps, Figs. 22-28, Pls. XXIV and XXV) arises and runs for- 
ward under the external carotid, or under the mandibular branch 
of that artery. Immediately in front of the lateral wing of the 
parasphenoid it crosses above the ramus palatinus posterior 
facialis, as that nerve issues from the palatine canal by its fora- 
men, and, turning inward and forward, passes through a small 
foramen (epsfr, Figs. 9-15, Pls. XXI and XXII) in the turned- 
up lateral edge of the thin layer of cartilage that forms the 
bottom of the passage leading from the eye-muscle canal to the 
orbit, and enters that passage opposite the basisphenoid. Here, 
in larvae and probably also in the adult, a communicating branch 
is sent to the internal carotid, the branch corresponding to and 
