1 88 ALUS. [Vol. XVIII. 



Myology. 

 I. Muscles of the Eyeball. 



The eyeball of Scomber is large, and the muscles that operate 

 it well developed. In addition to the six usual muscles there is a 

 rudimentary muscle associated .with, and apparently a part of, the 

 rectus internus. 



The Obliqui Muscles (Figs. 52, 61 and 66) arise, on each side 

 of the head, at the anterior part of the orbit, from the lateral sur- 

 face of the membranous interorbital septum. The surface of 

 origin of the obliquus superior lies immediately ventral to the ex- 

 posed, orbital part of the nervus olfactorius, the surface or origin 

 of the obliquus inferior lying immediately ventro-posterior to it. 

 A small part of the inferior muscle extends, at its insertion, up- 

 ward and forward around the inferior edge and then along the 

 anterior surface of the superior muscle, and reaches to the level of 

 its dorsal edge. 



The obliquus superior is inserted on the eyeball close to the' 

 insertion of the rectus superior, there lying immediately dorsal 

 to the latter muscle, and hence superficial to it. The obliquus 

 inferior is similarly inserted close to the insertion of the rectus 

 inferior, lying immediately ventral and superficial to it. The 

 four muscles all widen and become tendinous at their insertions. 

 Each pair, at its insertion, is covered superficially, that is dorsally 

 or ventrally as the case may be, by a thin and transparent but 

 strong membrane, which arises on the eyeball, near the edge of 

 the cornea, and is inserted on the outer surface of each of the 

 two muscles of each pair. 



The Recti Muscles all arise at the hind end of the orbit, or 

 in the eye-muscle canal. The rectus superior arises from the an- 

 terior edge and end of the horizontal membrane that separates the 

 eye-muscle canal into dorsal and ventral parts, and is inserted, 

 by a tendinous end, close to the obliquus superior, as already 

 stated. The rectus inferior arises partly from the membranous 

 interorbital septum, between the nervus opticus and the anterior 

 edge of the basisphenoid, and partly from a ligament or tendon, 

 that arises from the dorsal end of the shank of the basisphenoid 

 and runs forward and outward along: the hind edge of the muscle. 



