No. 3.] MUSCLES AND NERVES IN AMIA CALVA. 739 
2. The canalis transversus of selachians is, in Amia, a groove 
extending transversely from orbit to orbit, immediately in front 
of the transverse, cartilaginous bar that marks the anterior 
limit of the eye-muscle canal, and immediately in front of the 
two ossifications of that bar, which are said to represent, in 
Amia, the basisphenoid of teleosts. 
The eye-muscle canal of Amia and teleosts is not, there- 
fore, the canalis transversus of selachians, as Sagemehl con- 
cluded it to be. In Amia it is a cavity or space formed in late 
larval stages around the hypophysis cerebri and saccus vascu- 
losus ; and entrance to it, for the muscles of the eye, has been 
acquired through the foramen of the nervus abducens, or along 
a canal which serves for the passage of an important ophthal- 
mic vein. This vein arises from the under surface of the 
hypophysis, in connection with the corresponding vein of the 
opposite side of the head, and is almost directly continuous, 
anteriorly, with another vein, which arises from the choroid 
gland. Both veins are branches of that part of the orbital 
venous sinus that lies in the upper, lateral chamber of the eye- 
muscle canal. 
3. The internal carotid artery enters the cranial cavity 
through a special canal which traverses the basis cranii along 
the median edge of the basisphenoid of its side of the head. 
The basisphenoid of Amia thus lies lateral to the artery, while 
in Scomber and Perca it lies median to it. While traversing 
its special canal, the artery, in Amia, sends a communicating 
branch to the efferent pseudobranchial artery, and in the 
cranial cavity, after giving off optic and olfactory branches, it 
forms a circulus cephalicus opposite the auditory region and 
behind the lobi inferiores. 
4. The external carotid artery enters the upper, lateral 
chamber of the eye-muscle canal by a special foramen through 
the petrosal, but does not, so far as could be determined by 
sections, enter or send any branches into the cranial cavity 
proper. Branches of it issue from the eye-muscle canal with 
branches of the trigeminus and facialis, which they accompany. 
5. The efferent pseudobranchial artery enters the orbital 
opening of the eye-muscle canal by a special foramen, the 
