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H. W. NORMS AND SALLY P. HUGHES 



anteriorly around the posterior border of the rectus jventralis, 

 the anterior one entering and innervating the muscle and the 

 posterior one running across the ventral border of the muscle 

 and parallel to the truncus infra-orbitalis (figs. 7 to 9, 15 to 17, 

 and 21). This relation to the latter nerve is maintained *until 



the oculomotor branch terminates in the obliquus ventralis 

 muscle (figs. 5 to 9, 15 to 17, and 21). In this anterior course 

 the nerve passes ventral to the optic nerve. The relations of 

 the oculomotor nerve to the ciliary plexus will be described later. 

 The trochlear nerve leaves the brain in the fashion character- 

 istic of selachians: on the dorsal wall of the midbrain just an- 



