JOURNAL OF COMPARATIVE NEUROLOGY. Vol. 



Fig. 21 



Caudal Protriinon of 

 Fourth VenUtclt 

 (closed) 



Velum Med. Inf V 



3 



1 Cerclhihim 



\ 



Arachnoid 



,^~, Caudal Protrusion ol 



■ ^^- - - F..u,th Ventricle 



Velum. Med. Inf. 



Velum. Med. Sup. 



J^^^^"^- 



1 



Fig. 22 



'A 



Fia 



Caudal Protrusion of 



Fourth Ventricle 



( open ) 



Sec. Rhomboidal Lip 



.-^X 



Fig. 23 



Fig. 24 



ntriele Myelocoele 



Fig. 25 



•^' 



