xjsteology of the //ear? o/" Ilatteria. 309 



labota, by a simple suture. Tlie inner surfaces, wliich are 

 el(!vateJ into the paired crest, are very broad, but perfectly 

 flat, and are tirndy united to;;etiier by tlie cartilaginous tissue 

 wliieli is enibeddetl between them. 'J'he l.ni;e jiarietal torainen, 

 which is always of an oval shai)C, is in all the nine liitten'a 

 skulls which I have examined formed by the two halves of 

 the parietal alone, and the frontals contribute in not the 

 slightest degree to its limitation. The processus parietales 

 are fairly long, it is true, but do not reach the processus 

 paroticus of the parietal any more than in the case of the 

 majority of lizards, but attach themselves to the outer and 

 inner surface of the superior posterior process of the supra- 

 temporal. Each processus parietalis is indeed divided into a 

 longer posterior and a shorter anterior lamina, between which 

 the lower border of the posterior superior process of the supra- 

 temporal is wedged in. 



IV. 



The Vomer. — Baur* was the first to aimounce the interesting 

 fact that he had f(Mind in a young Ilatteria a distinctly deve- 

 loped tooth in the centre of each half of the vomer. A 

 communication was subsequently published by Howes t as 

 to further cases of the dentition of the vomer in Ilatteria. 

 Out of nine specimens he found that the vomer was toothed 

 in four cases, while five were toothless. Of the former, three 

 possessed a tooth on each half of the vomer, while in the 

 case of the fourth specimen a tooth was develoj)ed upon the 

 right half of the vomer alone. These teeth, however, had 

 not broken through the mucous membrane of the palate, as 

 Howes was able to convince himself in the case of two indi- 

 viduals, but their tips were covered by it, so that they were 

 not visible in the cavity of the mouth : — " its apex was 

 exposed, but it could not in any sense be said to project into 

 the cavity of the mouth." And with regard to the second 

 example he writes : — " In the other specimen the insignificant 

 vestiges of the teeth, which were present, lay wholly beneath 

 the mucous membrane, which completely covered their 

 apices." 



Among the nine Hatteria skulls examined by me I found 

 teeth upon the vomer in only one, while the remaining eight 

 exhibit no trace of such a dentition. In the toothed specimen 

 the right half of the vomer possesses two teeth, the left, on 



* G. Baur, " Osteologische Notizen liber Reptilieu, I. Rhynclio- 

 cephalia," Zool. Anzeiger, ix. Jahrg., 1886, p. 685. 

 t G. B. Howes, Troc. Zool. Soc. Lond. 1890, part iii. p. 358. 



