1870. ] LANKESTER—-NEWER TERTIARIES OF SUFFOLK. 497. 
nensis in the Norfolk stone-bed, resting on the old chalk land-surface 
at Horstead, which specimen was not preserved, but of which ho 
obtained two molars from the owner of the pit in which the bones 
were found. 
The relative abundance of the remains of Mastodon in the Norfolk 
and Suffolk beds is important. In the Norfolk stone-bed Mastodon 
arvernensis is undeniably very much more abundant than in the 
Suffolk bone-bed. This was sufficiently evident before the Suffolk 
area had been so largely worked for the phosphatic nodules. Now 
that the Suffolk bed has been carefully sifted and turned over for 
so many acres, there is danger of overestimating the abundance of 
its mammalian fauna, as compared with that from Norfolk. Teeth 
of terrestrial mammalia are of the extremest rarity in the Suffolk 
bed; and it is only because of the high price offered for them, and 
the constant operations of the ‘ coprolite-diggers,” that so many of 
them have been found. Comparing equal areas of exploration, the 
molars of Mastodon arvernensis are very much more abundant in 
Norfolk than Suffolk. In the Norfolk stone-bed the local collectors 
find that Mastodon is about twice as abundant as Llephas meridionalis, 
whilst Hgwus and species of Cervus are more abundant than either. 
A fact of importance with regard to the occurrence of Mastodon 
arvernensis in the Suffolk bone-bed is, that molars of this animal 
have been obtained from the bed with the soft bony fangs adherent, 
whilst in the case of nearly all other associated mammalia the 
enamel crowns only are found. 
It is important to notice that the bones of terrestrial mammals are 
almost unknown in the Suffolk bone-bed, whilst they are abundant 
in the Norfolk bed. It is also necessary to bear in mind that though 
the Suifolk bone-bed occurs below the Coralline Crag as well as 
below the Red Crag, yet it has not been proved that the mam- 
mals common to the Norfolk and Suffolk beds, viz. Mastodon arver- 
nensis, certain species of Cervus and Equus, are found in the bed 
when below the Coralline Crag. A Mastodon tooth which I have 
seen from that situation is not Mastodon arvernensis, but belongs 
to the Trilophodont species to be described below. 
These, being the facts of the case, it is well simply to state the 
hypotheses by which we may account for the occurrence of Mastodon 
arvernensis,—in Norfolk on the one hand, associated with Hlephas 
meridionalis ; in Suffolk on the other hand, in most intimate con- 
nexion with Upper-Miocene mammals. 
1. Seeing the very fragmentary nature of the remains found in 
both the Suffolk and Norfolk bone-beds, we might suppose that the 
absence of Hlephas in the Suffolk bed, and of Miocene forms in the 
Norfolk bed, is due to imperfect knowledge of the contents of the 
beds, which may constitute but one fauna. This is negatived by 
the improbability of such an association of forms to constitute a 
fauna as we should then get, and by the fact that the Suffolk bed 
at least has been remarkably well searched. 
2, Another explanation might be found in regarding Mastodon 
arvernensis as an annectant form, one which lived first with a Mio- 
