'372 Transactions of the South African Philosophical Society. 



These are named by van Bemmelen the " postfrontale (orbito- 

 sphenoidei) " and the " parietale-laterale." As both are apparently 

 membrane bones it is likely that the anterior is the reptilian post- 

 frontal and the posterior the postorbital. At the inner and anterior 

 part of the orbit there is a bony plate which may be the prefrontal. 

 It was believed to be so by Seeley, who apparently discovered it 

 as a distinct element. Van Bemmelen does not apparently believe 

 it to be distinct from the frontal, but in two of his illustrations he 

 figures it as distinct. Until further work has been done to the 

 structure of the skull in the young Monotremes the question of 

 whether there is a distinct prefrontal must remain as not definitely 

 settled. 



QuADBATE. 



I have elsewhere given reasons for believing that the mammalian 

 quadrate became lost in the glenoid cavity, at least as a bone. In 

 most mammals there is a distinct interarticular cartilage which may 

 represent it, but in only one known mammal is there a bone. This 

 is in Pedetes, the Cape- jumping hare. In it there lies in the front 

 of the glenoid cavity a small flattened oval bone measuring 

 2 mm. x 1 mm. It is invariably present, but it is likely to be lost 

 if the skull has been macerated. I regret that I have had no 

 opportunity of examining the condition of the parts in the young 

 animal, but hope to have ere long. It is just possible that the bone 

 may prove to be something else than the quadrate, but it is difficult 

 to see what else it can be. It may turn out to be a sesamoid bone 

 in connection with the external pterygoid muscle, but as it is in the 

 same position as the quadrate in the Cynodont reptiles the prob- 

 ability seems to be that it will prove to be a true quadrate bone. 



There are evidences of one or two other bones in the mammal 

 of interest. The ossicle of the caruncle in the young Mono- 

 tremes is probably the internasal process of the premaxillary. 

 I believe there is evidence of a distinct angular in the lower jaw 

 of Ornithorhynchus, but this and some other points require further 

 investigation. 



