562 Geological Society: Anniversary Address, 1843. 
the value of such microscopic researches is great; but if the five 
animals are grouped as one, then such mode of observation is of no 
value in palzontological science. 
Professor Owen had previously expressed opinions at variance 
with those of Drs. Hayes, Godman and Grant and Mr. Nasmyth, 
and his views have been supported within these walls by my pre- 
decessor, Dr. Buckland. Pointing out certain mistakes in the set- 
ting up of the Missourium, as exhibited in the Egyptian Hall, he 
compares the fossil with all forms with which he was acquainted ; 
and, showing that it must have belonged to the Ungulata, he judges 
that the enormous tusks of the upper jaw constitute it a member of 
the proboscidian group of pachyderms, and that the molar teeth 
prove it to be identical with Zetracaulodon or Mastodon giganteus. 
He argues that the genus Tetracaulodon was erroneously founded 
upon dental appearances in the lower jaw of a very young pro-— 
boscidian, and that Mr. W. Cooper was correct in suggesting that 
the Tetracaulodon was nothing but the young of the gigantic Mas- 
todon, the tusks of which were lost as the animal advanced in age. 
A comparison of the whole of M. Koch’s collection produced the 
result in Mr. Owen’s mind, that, with the exception of a few bones 
of the Alephas primigenius (Mammoth), all the other remains of 
proboscidean pachyderms in it belong to the Mastodon giganteus. 
The remains of other animals found by M. Koch are referred by 
the Hunterian Professor to Lophiodon, Mylodon Harlani, Bos, 
Cervus, &c.; and in respect to the Mastodon giganteus he expresses 
his conviction that it had two lower tusks originally in both sexes, 
and retained the right lower tusk only in the adult male. Although 
unable to form a correct judgement on the probable structure of 
those extinct quadrupeds, I may call your attention to a recent 
work of Mr. Kaup, whose striking discovery of the Deinotherium 
is familiar to you, and who now seems to advocate, from perfectly 
independent sources of evidence, the same views as Professor Owen 
concerning the osteology and generic characters of the Mastodon 
founded upon the comparison of a series of bones and teeth belong- 
ing to the Mastodon longirostris, more numerous and complete than 
even those of the Mastodon giganteus. 
Mylodon.—One of the most brilliant, and, I venture to say, not 
the least durable of the researches in paleontology, remains to be 
mentioned in the description of the Mylodon robustus, a new species 
of gigantic edentate animal, accompanied by observations on the 
affinities and habits of all Megatherioid animals. After a sketch 
of the labours of Cuvier, who first described the huge Megatherium 
_and pointed out its analogy to the family of Sloths and Armadillos, 
of the succeeding writings of Jefferson and Harlan upon the genus 
Megalonyx, of Dr. Lund on the Ccelodon and Sphenodon of Brazil, 
and of his own researches which established the Mylodon and Sce- 
lidotherium, Professor Owen proceeds to describe the megatherioid 
animal which he has named Mylodon robustus. 
Of the purely anatomical descriptions, it is not my province to 
speak, and referring you to the work in which, through the en- 
