NEW FACTS CONCERNING BOTHR1OLEPIS. 



121 



just in front of the extra-lateral. It should be regarded as be- 

 longing to the anterior dorsal margin of the head, Fig. I. But 

 it is movable and is nearly always folded over on to the ventral 

 surface, Fig. 3. It is marked with a sensory groove, probably 

 a continuation of the anterior vertical one, although it does not 

 appear to be exactly in line with it. 



The median plate of the ocular opening is nearly perforated 

 by a deep pineal foramen, often indicated by a low tubercle on 



?P 



FlG. 6. Ocular and olfactory plates, in position with part of the rostral and lat- 

 eral plates removed, a.s, anterior sclerotic; J.s, dorsal sclerotic; e, ethmoid; l.e, 

 lateral arm of ethmoid; l.s, lateral sclerotics ; m, membrane; o, corneal surface of 

 eye ; <>/, olfactory opening ; /, two pineal eye pits on under side of post-orbitals ; 

 p.p, pineal tubercle on outside of pineal plate ; p.s, posterior sclerotics. X about -,% 



the outer surface, Fig. 6. A pair of similar pits, but not quite 

 as deep and without any surface indications of their presence, are 

 clearly shown on the inner surface of the small post-orbital. 

 There is every reason to regard these three pits as similar in 

 character and as indicating the presence of a tri-ocular median 

 eye. 



