360 PROF. G. B. HOWES ON HATTERIA. [May 6, 



ridges in ail the skulls which he had examined. Alluding to the teeth 

 themselves, he said he had been able to examine them in relation 

 to the mucous membrane of the roof of the mouth in two specimens. 

 In one of these, it so happened that the teeth were unequally deve- 

 loped, that of the right side being the larger. The individual 

 tooth alluded to was the largest he had observed ; its apex was 

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

 cavity of the moutli. The tooth of the opposite side, which had 

 more nearly the proportions observed in other specimens, was 

 wholly buried beneath the mucous membrane, in the manner of a 

 vestigial structure. In the other specimen the insignificant vestiges 

 of the teeth wliich were present lay wholly beneath the mucous 

 membrane, which completely covered their apices. 



In one specimen there was present on the right side (fig. 2, p. 359) 

 a small tooth-like tubercle in continuity with tlie base of the vomerine 

 tooth. He was unable to say definitely whether the former repre- 

 sented a distinct tooth or a dismembered portion of the larger one. 



Commenting upon the aforementioned facts, he pointed out that 

 in the recently discovered Palceoliutteria of the Permian (Credner, 

 Zeitschr. deu'tsch. geolog. Gesellsch. 1888, p. 490), which animal 

 unmistakably connects theliving Ilatteriavixih the Sfegocephalia, the 

 vomers were markedly dentigerous. It becomes therefore a question 

 whether, in Hatteria, we are dealing with a vestigial or a reversional 

 condition of the same. Baur's observation alluded to would seem 

 to indicate that vomerine teeth appear in the young individual and 

 disappear with advancing age. On the other hand, the most 

 marked development of the individual tooth wliich Prof. Howes had 

 observed was realized in a senile old male (v.), while Mr. Boulenger 

 had failed to find teeth in a specimen much younger than that of 

 Baur'. The presence of a minute tooth on one side (ii.), where that 

 of the other was well defined, was suggestive of a pecuHar mode of 

 disappearance of paired vestigial structures known elsewhere (which 

 he illustrated by the exhibition of a Pigeon's intestine in which 

 but one of the two familiar caeca was present), and therefore indicative 

 of the vestigial nature of the vomerine teeth. The observations 

 of Boulenger and Baur did not appear to him to be contradictory, 

 as vestigial structures are well known to frequently appear late. 



So far as the evidence afforded by his tooth-bearing specimens 

 went, the tooth of the left side was the more variable, that being 

 either small or absent, while the tooth of the right side was well- 

 developed or even duplicated (?). It would therefore appear that 

 the teeth in question are not only vestigial but that they are, at the 

 present time, undergoing suppression from left to right. 



Prof. Howes finally directed attention to the fact that those 

 individuals possessed of teeth, in which he had been able to determine 

 the sex, were males, and alluded to the desirability of information 

 concerning the vomer of Colenso's supposed new species of Hatteria 

 (Spkenodon diversum, Trans. New Zealand Instit. vol. xviii. p. 118, 

 1886). 



' In the possession of Sir W. Buller, approximate total length about 120 mm. 



