COMMUNICATIONS 
TO THE 
MONTHLY MEETINGS 
OF THE 
YORKSHIRE PHILOSOPHICAL SOCIETY, 
1889. 
PL A TYCRCER OPS RICIIARDSONI. 
The specimen, of which a view is given in fig. 1 of Plate 
I., is one of the treasures of the Museum, and is absolutely 
unique. It was obtained not later than 1854 from the 
London Clay of Herne Bay, in Kent, and was described in the 
British Association Report for that year, by Mr. E. Charles worth, 
under the name of Platychoerops Richardsoni; it was again 
described, with a figure, by Sir Richard Owen, in the Geological 
Alagazine for 1865, as Miolophus planiceps. The specimen 
consists of the middle portion of the skull of a small mammal, 
of about the size of the common fox, which has been 
considerably fiattened by pressure. It shews the anterior part 
of the skull, the commencement of the zygomatic arches, the 
frontal region, and a considerable portion of the palate. Five 
teeth are preserved, namely, the last and penultimate ones on 
both sides, and on the right side the fourth tooth from the hinder 
end of the series. These molariform teeth (fig. la^) have fiattened 
crowns, carrying three cusps or tubercles arranged in a triangle, 
and an internal ledge or cingulum. The outer cusps have their 
external surface somewhat fiattened and inclined inwardly, 
while the inner cusp is somewhat Y-shaped. This type of tooth 
belongs to that modification which Professor Cope has proposed 
to call the trituhercular —a type very common among the 
mammals of the early Eocene. In advance of the next anterior 
tooth now remaining, there were evidently toothless intervals in 
the jaw, but whether there w^as a tooth immediately in contact 
with the first now remaining cannot be determined. So far as 
can be seen, the bony palate appears to have been prolonged 
for some distance behind the last tooth. 
