42 PROCEEDINGS OF THE GEOLOGICAL SOociIETy. [June16 
of the lobes that they had been lost: the chamber was filled with the 
fine eocene sand, and by its size indicated a rather larger development 
of the tubercle e than the first and second molars. : 
Thus the dental. formula of the lower jaw of the present Mammal 
is proved to consist of three incisors, one canine, four premolars, and 
three true molars, in a continuous series in each ramus ; and we must 
conclude that they were opposed by the same number of teeth in the 
upper jaw. The detached premaxillary demonstrates in fact the 
number and shape of the incisors of that jaw; the crowns of these 
incisors being, as in the Anoplothere, somewhat larger than those 
below. The single-fanged tooth which I have described as the upper 
canine shows the same proportional superiority of size over that of the 
lower jaw, with a correspondence of form which leaves no doubt in 
my mind of its bemg the opposing tooth of such lower canine. There 
are wanting, therefore, to establish ex visu the entire dental series, 
only the first and second premolars of the upper jaw and the last true 
molar of the lower jaw, the germ of which had not been sufficiently 
calcified at the time of the animal’s death to yield satisfactory evidence 
of its true form. 
The dental formula therefore of the genus Dichodon is :— 
foo) Stil) ei toe 
en Pome ho remy ater are Tames 
From the trenchant character of the ridges and the sharp points of 
the lobes of all the teeth, which in the molar series are bristled with 
cusps like those of some Insectivores, the food of the Dichodon would 
seem to have been of a peculiar character, perhaps not exclusively of 
a vegetable nature, but different from that of any of the small Rumi- 
nants or Pachyderms of the existing creation. From the number 
and sharpness of the poimted cusps of the teeth in the present species, 
I propose to call it Dichodon cuspidatus. 
DESCRIPTION OF PLATE IV. 
Fig. 1. Portion of lower jaw of Paloplotherium, with the four deciduous molars 
and first permanent molar, one canine and one incisor. 
Fig. 2. Outside view of the lower jaw and teeth and parts of the upper jaw and 
teeth of Dichodon cuspidatus, nat. size. 
Fig. 3. Grinding surface of most of the teeth of the upper jaw of ditto. 
Fig. 4. Grinding surface of the teeth (M 3 excepted) of the under jaw of ditto. 
Fig. 5. Inside view of the lower jaw and teeth and parts of the upper jaw and 
teeth of ditto. 
Fig. 6. Hind view of the crown of the second upper molar of ditto. 
Fig. 7. Grinding surface of second upper molar of Merycopotamus. 
In each figure, I 1, 2, 3, indicates the first, second and third incisors; C the 
canine; P 1, 2,3, 4, the premolars; M 1, 2 & 3, the molars. The letters of the 
lobes and cusps are explained in the text. 
= 44. 
3. Notice of the occurrence of Fossil Remains of the MEGACEROS 
HIBERNICUS and of CasTOR EUROPEUS in the Pleistocene deposits 
forming the Brick-fields at IL¥Forp and Grays-THURROCK, 
Essex. By Pror. Owen, F.R.S., F.G.S. 
Since the publication of my ‘ British Fossil Mammalia,’ two of the 
conclusions touching the so-called ‘ Irish Elk,’—-viz. first, that its re- 
