'350 Annals of the South African Museum. 



yet been mentioned. This is the ethmoid. It lies under the frontal, 

 and is badly shown in the present skull. 



There remains only one other bone to be discussed, namely, the 

 dumb-bell shaped bone lying between the quadrate and the basi- 

 occipital process. In the present skull it is beautifully shown, as 

 can be seen in Fig. 2. Seeley has left it unnamed in the illustra- 

 tion, and hitherto there has been doubt as to its determination. I 

 have long been of opinion that it was the tympanic, but I have just 

 discovered that this is not so. There is now no doubt that the ear 

 capsule extends down the basioccipital process and that the fenestra 

 ovalis is situated at the side of the lower end of the process and that 

 it is covered by the end of the bone in question. There can there- 

 fore be no longer any doubt that the bone is a true stapes. Else- 

 where I shall give a detailed account of the structure of the 

 Anomodont ear. In Oudenodon kolbei the stapes is, when viewed 

 from below, a somewhat dumb-bell shaped bone, but being irregu- 

 larly rhomboidal in shape it measures across the one pair of opposite 

 angles 30 mm., and across the other pair 23 mm. Across the 

 narrowest part of the middle it measures 12 mm. When the bone 

 is viewed from behind it is seen to be much flattened, the middle 

 part being only 4 mrn. in thickness. 



The following are the principal measurements of the skull, allow- 

 ance being made for the slight distortion. 



Greatest length from occipital condyle to front 



of beak 228 mm. 



Greatest length from beak to back of squamosal 27-i 



Width of frontal region 36 



Width of skull behind postorbital bar 170 



Greatest width across squamosals, about 230 



Greatest width of palate 56 



Length from orbit to front of beak 65 



Length of orbit 55 



Width at narrowest part of parietal region 35 







Addendum. Since the above was written there has appeared 

 Prof. Jaekel's book entitled "Die Wirbeltiere," in which he gives 

 three figures of the skull of Ondenodon kolbei. His interpretations of 

 the bones agree in the main with those here given. He recognises 

 the distinctness of the quadrato-jugal. The bone which has been 

 called preparietal by Seeley and myself Jaekel regards as the 

 unpaired parietal. The bones which we regard as the parietals he 



