No. 3.| MUSCLES AND NERVES IN AMIA CALVA. 52 i 
(No; 193, Fig. 12, and: No: 116,,Fig: 1).’- In: Plasiostomata 
the internus arises with the other recti at the hind end of the 
orbit, but both muscle and nerve lie above the opticus, while 
in ganoids and teleosts they both lie below it. In the young 
of Scyllium the rectus internus is innervated by an anterior 
branch of the superior division of the oculomotorius (No. 77, 
p. 88). In the adult Scyllium this anterior branch may 
become somewhat widely separated from the branch to the 
superior rectus, two superior branches thus arising from the 
main nerve, — the proximal one of the two going to the rectus 
internus (No. 113, Fig. 10). In Mustelus laevis the oculomo- 
torius, after sending branches to the internal and superior recti, 

rocms ad rs 
Cur 1.— Top view of left eyeball of Galeus canis. oft, ophthalmicus superficialis trigemini ; os, 
ebliquus superior; ve, rectus externus ; ~z¢, rectus internus; vocms ad rs, branch of superior 
division of oculomotorius to rectus superior ; ~s, rectus superior; 7, trochlearis. 
perforates, according to Schwalbe (No. 113, p. 185), the rectus 
internus near its upper posterior edge, while according to 
Tiesing (No. 123, p. 79) it perforates the rectus superior. It 
then runs downward behind the rectus inferior, and forward 
below that muscle, and ends in the obliquus inferior. In 
Galeus canis I find a similar arrangement (Cut 1). In Scyl- 
lium catulus (No. 113, p. 187) the inferior division of the 
oculomotorius penetrates the rectus superior near its hind 
edge, and in Raja batis (No. 113, p. 188, and No. 123, p. 80) 
it runs down behind that muscle, in both cases turning for- 
ward below the rectus inferior. In Chimaera, judging from 
Schwalbe’s figure alone (No. 113, Fig. 12), it runs down in 
front of the rectus superior, while in Callorhynchus (No. 116, 
Fig. 1) it apparently lies behind that muscle. 
