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Show 360 PROF. G. B. HOWES ON HATTERIA. [May 6, ridges in ail the skulls which he had examined. Alluding to the 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 developed, 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 mouth. 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 which 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 the base of the vomerine tooth. He was unable to say definitely whether the former represented a distinct tooth or a dismembered portion of the larger one. Commenting upon the aforementioned facts, he pointed out that in the recently discovered Palaohatteria of the Permian (Credner, Zeitschr. deutsch. geolog. Gesellsch. 18H8, p. 490), which animal unmistakably connects theliving LLatteria with the Stegocephalia, 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 which Prof. Howes had observed was realized in a senile old male (v.), while Mr. Boulenger had failed to find teeth in a specimen much youuger than that of Baur1. The presence of a minute tooth on one side (ii.), where that of the other was well defined, was suggestive of a peculiar mode of disappearance of paired vestigial structures known elsewhere (which he illustrated by the exhibition of a Pigeon's iutestine 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 (Sphenodon diversum, Trans. N e w Zealand Instit. vol. xviii. p. 118, 1886). 1 In the possession of Sir W . Buller, approximate total length about 120 mm. |