OF THE EYE MUSCLES IN MARSUPIALS. 



315 



prolongation into which runs nerve VI and becomes continuous 

 with the anterior part. The latter turns round ahnost at right 

 angles and runs out laterally immediately behind the postero- 

 lateral wall of the head-cavity (text-figs. 9 & 12, r.e.). It tapers 

 ventrally, its lower outer end lying close against the inner 

 portion of the m. obliquus inferior, the two being connected 

 through two or three sections. 



Text-fiafiu'e 11. 



M^W 





HB 



9.c.a. 



^CIl./ 





H>^\~'':^: \ 



:^ ^Y/;v^ 



^,Cfr'"'^"'^r '« 





' "' v^tw f^'^- '^P^^ 



TricJiosurus vulpecida. G.L. 7'25 mm. (XII A. '02). 



Longitudinal section (S 9-3-9), passing througli tlie medial side of the right head- 

 cavity {r.h.c.) to show the proliferation from the posterior wall (pm.+jjl.) 

 and the postero-dorsal portion (r.b.) of the abducens muscle-mass. X 110 and 

 reduced by j. 



ff.c.a. =arteria cerebri anterior. I^J?.= fore-brain. a.f.j.=arteria carotis interna. 

 iri?. = hind-brain. IIl.=oculomotor nerve. 



The trigeminal nerve has now both a supra-orbital and a 

 naso-ciliary branch, running forwards above the bulbus, the 

 naso-ciliary lying on the outer side of the dorsal end of the 

 cavity (text-figs. 9 & 13, n.c.V.). 



The primordium of the m. obliquus superior is best seen in the 

 longitudinal series (text-fig. 13, o.s.). It begins a,s a collection 

 of cells above and anterior to the optic cup and, extending along 

 the venti-al and ventro-lateral sides of the supra-orbital nerve, 



Proc. Zool. Soc— 1915, No. XXIII. 23 



