Mastodon is likely to be is the Miocene M. tapiroides (M. turacensis, Pom.), which also belongs to the Trilophodont section, and has simple valleys. The molars of M. tapiroides have a very marked cingulum, and are broader than those of M. Borsoni; whilst the ridges are not so high relatively as in that species. A small oblique plication running vertically on the sides of the transverse ridges is, however, considered by M. Lartet (Bull. Soc. Geol. France, 1859) its most distinguishing feature. Now, Mr. Baker's molar (Pl. XXXIV. figs. 1 & 2) has shorter ridges than M. Borsoni, is wider than specimens of the corresponding tooth of M. Borsoni which I examined in Paris and in Le Puy, and has a considerable development of cingulum, which, though not nearly so large as that of M. tapiroides is yet larger than any presented by M. Borsoni. At the same time, Mr. Baker's specimen, and all the fragments except that drawn in fig. 4, have no trace of the oblique vertical fold characteristic of M. tapiroides. A decided indication of this fold is, however, present in Mr. Canham's fragment drawn in fig. 4 (t r), and it is a question how far this is decisive of a specific relation to M. tapiroides. We have not at present the material for deciding the question, though this particular fragment (fig. 4) is referable to that species. M. Lartet, however, informs me that he has seen from other localities evidence of a form intermediate between M. tapiroides and M. Borsoni, and the specimens from the base of the Crag may belong to such a form. The posterior talon seen in figs. 1 and 2 is also preserved in the two specimens in the British Museum, and has a very constant form.
All the specimens of this Trilophodont form, excepting Mr. Baker's, are mere fragments, and most are much water-worn, which is significant of their history, and contrasts strongly with the condition in which the teeth of Mastodon arvernensis occur ; so much so that one is not disposed to regard the two species as certainly contemporary. The fragments and water-worn bits of Rhinoceros-teeth may be more consistently associated with this new Mastodon ; and on the whole it seems probable that we must assimilate this new Trilophodon to the Miocene rather than the Pliocene species.
I am aware that Mr. C. B. Rose some years since obtained a fragment of a Mastodon-tooth from gravel-beds, which he considered to be M. Borsoni ; but the specimen and its history appear to be too imperfect to throw any light on the Trilophodont species from the Suffolk bone-bed, one specimen of which, be it remembered, is of pre-Diestien age.
V. List of Species of Terrestrial Mammalia from the Suffolk Bone-bed, with reference to the number of Specimens and the Collections containing them.
There is, and has been for some years, in that district of Suffolk where the so-called " coprolites " arc dug, a remarkable eagerness to obtain and preserve the teeth of Mastodon and other mammals found in the bed. Very high prices are given for these teeth (in some cases several pounds), and accordingly many of the most interesting
