54 ALUS. [Vol. XVIII. 



factory, the dense connective tissue that separated certain of the 

 bones, staining with ahnost the same colour and intensity as the 

 cartilage itself. Skulls slightly boiled, and examined while 

 fresh, were then tried with better results, but the most satisfactory 

 results were obtained by a process of natural staining which con- 

 sisted in simply leaving to macerate, for a short time, a fresh 

 head that had been slightly boiled. The cartilaginous parts of the 

 skull, so treated, soon turned a dark rich brown, the other tissues 

 remaining unchanged. 



The postorbital remnants of the chondrocranium are in part ex- 

 posed, either on the outside or the inside of the skull, and in part 

 entirely enclosed between the edges of the adjoining bones. The 

 exposed interspaces are six in number : a dorso-median one lying 

 immediately posterior to the epiphysial ridge ; a ventro-median one 

 at the base of the shank of the basisphenoid ; a dorso-lateral one, 

 on each side, lying in the floor of the temporal groove and already 

 referred to ; and a ventral one, on each side, lying along the ventral 

 edge of the petrosal. The larger part of each dorso-lateral, or tem- 

 poral interspace is seen on the external surface of the skull, as is 

 also a- narrow, median line of the post-epiphysial one. The two 

 ventral interspaces are only visible on the internal surface of the 

 skull, or after the parasphenoid has been removed. They will all be 

 described in describing the bones related to them. No one of them 

 is, in any place, continuous with the antorbital cartilage. The post- 

 epiphysial cartilage and the small bit at the base of the shank of 

 the basisphenoid are, however, connected with the antorbital car- 

 tilage by the thick, membranous, interorbital septum, which should, 

 undoubtedly, be considered as a part of the primordial cranium 

 that has not chondrified. 



The persisting cartilagje of the anterior part of the chondro- 

 cranium is a continuous median piece with dorso-lateral, ventro- 

 lateral, and anterior extensions, these extensions forming parts 

 of the roof and floor of the antorbital processes, and the ventral, 

 median, and anterior portions of the rostrum. The cartilage 

 separates the three primary ossifications of the antorbital 

 region one from the other, and caps their several articular 

 processes. Its ventral surface is flat, forms the base of the an- 

 terior part of the chondrocranium, and is grooved, in the middle 



