162 



Annals of the South African Museum. 



which siirround a single bone undivided by any median suture. 

 Sutures are not traceable in the parietal boss ; but a short distance 

 behind it a median suture between the two parietals is visible. The 

 evidence thus points strongly to the conclusion that there is a single 

 median bone between the frontals and the parietals, forming at least 

 part of the boss around the pineal foramen. In the type of Eocyclops 

 longus there is no doubt that a median suture occurs just in front of 

 the pineal foramen ; and the question again arises therefore How 

 much stress can be laid upon the presence or absence of the pre- 

 pai'ietal ? It is just possible, of course, that in the South African 

 Museum specimen the suture in front of the foramen between two 



FIG. 40. Eocyclops longus, Br. Skull. No. 3425. x $ nearly. 



parietals may have been obliterated ; but the other sutures on the 

 skull stand out so clearly, and that between the parietals in their 

 posterior part is so obvious, that this does not seem a feasible solution 

 of the matter. It would seem much better to suppose that, although 

 in the smaller Dicynodonts the preparietal is a constant within any 

 one species and is constantly present or absent in the genus, in the 

 case of these very large and presumably somewhat aberrant forms 

 the bone is inconstant in character and is not of importance sys- 

 tematically. Certainly the three skulls S.A. Mus. 3425, type of 

 " Oudenodon magnus " and type of Eocyclops lonyus agree so closely 

 in other regards, as far as can be seen from the somewhat incomplete 

 descriptions, that this one difference can scarcely be held to be 

 sufficient to separate them generically. 



The skull from Graaff Reinet is in very fine condition and is worthy 



