265 



points out the general structure and peculiarities of the three princi- 

 pal Mastodontoid genera, — Mastodon, Tetracaulodon, and Dinothe 

 rium, — and gives the dental formula' of each of them. For the de- 

 termination of those of the two first named genera, Dr. G. states that 

 he has relied entirely on the splendid collection of Mr. Koch, which 

 affords ample means for the purpose. The results of his investiga- 

 tions coincide precisely with those arrived at by the author of this 

 communication, and which were presented to this Society, in a paper 

 read twelve years ago. As each has obtained his results from the 

 examination of an entirely different series of specimens, they mutually 

 confirm each other. 



The second paper is by Mr. Alexander Naysmith. This skilful 

 anatomist has made a microscopic examination of the structure of 

 the tusks of the Mastodon giganteum, Tetracaulodon Godmanii, T. 

 Kochii, T. tapiroides, and of the Missourium ; and he states that the 

 minute structure of all these five animals exhibit considerable varie- 

 ties. The peculiarities in the tusk of the Missourium, he adds, cer- 

 tainly indicate a distinct species. These results cannot but be re- 

 garded as extremely interesting, though it must be admitted, Dr. H. 

 remarked, that the actual value of these characters was yet to be de- 

 termined. Dr. H. reminded the Society of what he had stated on a 

 former occasion, that each tusk of the Missourium was in three pieces, 

 and that it was far from certain that they all had belonged to the same 

 animal, and therefore he must now express his regret that Mr. N. 

 had not examined a section of each of the three pieces, or at all 

 events had not stated in which piece the section he examined was 

 made, as the middle piece Dr. H. thought had been inserted, and that 

 to this was due the great length of the tusks and their peculiar curve. 



The third paper was by Mr. Koch, and contains the results of this 

 gentleman's researches, which in his opinion fully prove the Tetra- 

 caulodon to be a distinct genus. 



Dr. H. stated, that whilst he still conceives, as he has done from the 

 first, that the balance of evidence was in favour of the correctness of 

 that opinion, still it was due to truth and science, that false weights 

 should not be allowed a place in the scales, and therefore he felt it his 

 duty to correct one or two of the statements made by Mr. Koch, and 

 which are founded on careless observation. 



Mr. K. asserts that the Mastodon in the Philadelphia Museum is a 

 male, according to the construction and size of the pelvis, and the 

 magnitude of the tusks in the upper jaw ; yet there are no traces of 



