BY R. BROOM. 197 



posterior end of the capsule and the occipital cartilage is a 

 large foramen for the passage of nerves ix., x., and xi. The 

 auditory capsule is well developed^ but chondrification has only- 

 just begun, and most of the capsule is still in the procartilage 

 stage. It extends far up by the side of the brain, and merges in 

 the ill-defined band of procartilage which supports the lateral 

 wall of the brain. At the plane of the front of the auditory 

 capsule the basal cartilage is much narrowed, but on passing a 

 little forward it is found to again rapidly widen. The notochord 

 •ends near the point where the expansion begins. The expanded 

 portion is about double the width of the constricted, and, towards 

 the outer part of the expansion, there is a large oval foramen for 

 the carotid artery. Along the outer part of the expanded part 

 a,nd a little distance from it, lies an elongated, oval bar of carti- 

 lage unconnected with any other, and which, as it ultimately 

 develops into the alisphenoid bone, may be called the alisphenoid 

 cartilage. A little in front of the plane of the carotid foramen, 

 the basal cartilage becomes again narrowed, and, in the middle 

 'line, there is an oval foramen of about the same size as that for 

 jthe carotid artery, which represents the pituitary fossa. In front 

 -of the fossa, for a considerable distance, the basal cartilage is 

 very manifestly seen to be composed of two trabeculae conjoined 

 in the middle line. In the posterior nasal region the double 

 -^origin of the cartilage becomes less marked, and from here forward, 

 to near the front of the snout, there is little or no evidence of a 

 double origin. Wliether the whole of the nasal septum is trabe- 

 cular in origin is doubtful, but the base, at least, is pretty 

 manifestly the anterior continuation of the trabeculse. The nasal 

 -capsule is very imperfectly chondrified, but the arrangement can 

 be made out fairly easily. It may be described as a cylindrical 

 structure with three openings, one at the anterior end looking 

 ■outwards, the anterior nasal opening; a second opening down- 

 wards into the mouth, the internal nares ; and a third opening 

 upwards and backwards, the opening for the nerves. The inferior 

 'Oi)ening is bounded on the inner side by a strip of cartilage or 

 procartilage which runs along parallel to the base of the nasal 



