Nos. IAND2.] ANATOMY OF SCOMBER SCOMBER. 189 



The muscle is inserted close to the obliquus inferior in the manner 

 already described. The rectus internus arises from the mesial 

 part of the ventral surface of the anterior two thirds, approx- 

 imately, of the horizontal membrane of the eye-muscle canal. It 

 runs forward, ventral to the rectus inferior, and is inserted directly 

 on the eyeball, between the oblique muscles, without the interven- 

 tion of a tendinous end. A small but well developed tendon, is, 

 however, always found running forward from the distal end of 

 the muscle and having its insertion on the eyeball. Associated 

 with the rectus internus there is always a slender rudimentary 

 muscle which arises by a long tendon from the shank of the 

 basisphenoid, immediately dorsal to the point of origin of the 

 ligament related to the rectus inferior. This rudimentary muscle 

 runs forward along the dorsal edge of the rectus internus, close 

 to and parallel to that muscle, and, continuing forward beyond it, 

 widens considerably and is inserted in loose connective tissue that 

 covers the eyeball. The rectus externus arises from the lateral 

 walls of the eye-muscle canal, dorsal to the horizontal membrane 

 of the canal, its surface of origin beginning posterior to the 

 pituitary fossa and continuing backward to the extreme hind 

 end of the canal. The muscle turns outward as it issues from 

 the canal, and, near its insertion, becomes reduced to a tendinous 

 point which passes under the outer edge of the cornea and is 

 there inserted on the inner surface of the cornea and on the outer 

 surface of the sclerotic. 



The muscles are innervated in the same way that they are in 

 Amia, with the exception, only, of the order in which the branches 

 to the rectus internus and rectus inferior leave the inferior 

 branch of the oculomotorius. This will be fully described in 

 describing the latter nerve. 



2. Muscles Innervated by the A^ervits Trigeminus and Nenms 



Facialis. 



When the outer skin is removed from the lower portion of the 

 cheek, there is found immediately beneath it, between it and the 

 pigment -layer, a thin fibrous layer, the fibers of which radiate 

 upward from the lower, posterior corner of the mandible. The 

 fibers run upward and forward, directly upward, and upward and 



