1246 DR. ERIK A. STE>fSIO : NOTES 



are seen in text-fig. 1 (Y). After their exit tlirougli this foramen, 

 the trigeminus brancties proper, accompanied by the n. buccalis 

 lateralis, have evidently passed forwa,rd to the orbit laterally of 

 the alisphenoid wulst a,nd dorsally of the basipter3-goid process; 

 while the n. ophthalmicus lateralis immediately took a more 

 dorsal course, entering the canal {c.ophth.lat.) in the dorsal part 

 of the alisphenoid wulst and, soon after having left this, reaching 

 the roof of the orbit. As the canal {c.ophth.lat.) has a r;ither 

 small calibre, it seems to me most probable that the r. oplithal- 

 micus superiicialis did not pass through it, but ran independently 

 of the n. ophthalmicus lateralis as it does in Sturgeons and 

 certain Siluroids, and as it certainly did also in Sauriclithyids 

 {cf. Stensio, 1922 6; Workman, 1900, pp. 404-407: Herrick, 

 1901, pp. 201-203). The r. ophthalmicus profundus trigemini 

 or a somewhat equivalent nerve must apparently have been 

 formed already within the cranial cavity, from where it pierced 

 the pars lateralis of the sphenoid independently of the other 

 trigeminus branches (or their roots) through the canal V^ described 

 above {cf. Stensio, 1921, pp. 58-59. 93, 169-170 ; 1922 a, p. 183 ; 

 1922 &). 



The exit of the facialis nerve must, so far as one can judge, 

 have been situated somewhat postero-venti'ally of the trigeminus 

 exit, so that the r. palatinus facialis in its way do\'i'nwards and 

 forwards must have run first posteriorly and then ventrally to 

 the basipterygoid process before it I'eached the orbit {cf. Allis, 

 1919 a.; Stensio, 1922 «)• 



Of the exit of the n. abducens nothing is known with certainty, 

 but the nerve may perhaps have left the cranial cavity through 

 the trigeminus foramen {cf. Stensio, 1922 h). 



The olfactory nerve has fiom the anterior end of the cranial 

 cavity, as we shall see, entered an antero-ventro-laterally running 

 canal in the ethmoidal region. 



The opticus has left the cranial cavity far forwa.rd. It per- 

 forated the pars lateralis of its side somewhat anterior of the 

 middle of the length in a downward and forward direction, and 

 has reached the orbit strikingly low^ (II, text-fig. 1 ; PL I. 

 figs. 1, 2, 4) immediately dorso-caudally of the thinnest part of 

 the pars basalis of the sphenoid. 



Somewhat behind the opticus exit, but only slightly higher 

 than this, is found a,n oval foramen, which undoubtedly trans- 

 mitted the n. oculomotorius (III, text- fig. 1 ; PI. I. figs. 1, 2, 4). 



High up, lather near the cranial roof and appioximately 

 midway betw^een the opticus and oculomotorius exits, is found 

 the external opening of a fine canal (IV, text-fig. 1 ; PI. I. 

 figs. 1, 2, 4), which must undoubtedly have transmitted the 

 n. trochleaiis. 



A rather wdde canal {v.cerehr.ant, text-fig. 1; PI. I. figs. 1, 2), 

 which is situated high up anterior of the opticus and trochlearis 

 exits, must probably have been traversed by the vena cerebralis 

 anterior {of. Stensio, 1921, pp. 168-169) on its way to the orbit. 



