A492 ALLIS. [Vou. XII. 
I. THE ORBIT, THE MUSCLES OF THE EYE, AND THE 
ASSOCIATED NERVES AND ARTERIES. 
1. Hye-Muscle Canal. 
Amia has, as already described by Sagemehl (No. 104, p. 214), 
a well-developed “Augenmuskelkanal”’ (emc, Fig. 11, Pl. XX1I), 
bounded in front and behind by transverse ridges of the car- 
tilaginous base of the skull. The posterior ridge lies near 
the hind edge of the petrosals, and bears on its summit the 
transverse processes of those bones. The anterior ridge is a 
specially developed structure (w, Figs. 9 and 11, Pl. XXI), 
called by Sagemehl a transverse ‘“ Wulst,” and by Shufeldt 
(No. 115) a transverse “bar” of cartilage. This bar is sharply 
marked off from the rest of the basis cranii by the Augenmus- 
kelkanal behind, and in front by a narrow but comparatively 
deep groove (cz) which extends transversely from orbit to orbit. 
At each end of the bar there is usually, but not always, a small 
ossification, the basisphenoid of Bridge (B&,S, Figs. 13, 14, and 
15, Pl. XXII), which in one large specimen, contrary to Sage- 
mehl’s statement (No. 104, p. 215), extended in part through 
the cartilage of the base of the cranium, so as to be seen on its 
under surface. In the same specimen the basisphenoid on the 
left side of the head extended forward across the transverse 
interorbital groove, bridging it or being perforated by it. In 
all the specimens examined the two ossifications were of unequal 
size, and they never touched each other at any point, a median | 
region of cartilage always separating them. 
At about the middle of the median edge of each basisphenoid 
there was in all the specimens examined a deep indentation, 
forming, with the adjoining cartilage, a canal (zc, Figs. 9, 10, 
14, and 15, Pls. XXI and XXII) through which, and not 
through the hypophysial fenestra as stated by Wright (No. 
133, p. 495), the internal carotid artery on each side entered 
the cranial cavity. From this canal, near its ventral opening, 
one, or sometimes two, small canals run forward and laterally 
through the bone into the tranverse interorbital groove, or 
into the extreme hind end of the orbit near it. From the free 
lateral edge of the bone the superior, inferior, and internal recti 
