162 
not universally effaced in species. To guard himself, however, from 
misconstruction, Mr. Williams adds, he believes entirely in the ex- 
tinction of genera and species; but at very distinct epochs, and in 
far thicker and more extended groups of strata than is imagined ; 
and that consequently the identification of strata must be regulated 
by a per-centage test similar to that applied by Mr. Lyell to the 
tertiary series. Lastly, he protests against the determination of 
the age of the Devonshire formations by reference to the structure 
of a foreign district. 
Dec. 18.—William Sidney Gibson, Esq., Essex Street, Strand, 
was elected a Fellow of this Society. 
A paper was first read, entitled ‘‘ Description of the fossil remains 
of a mammal, a bird, and a serpent, from the London clay,” by 
Richard Owen, Esq., F.R.S., F.G.S. 
The author commences by observing, that only a few months had 
elapsed since the highest organic animal remains known to exist in 
the London clay were those of reptiles and fishes; and that the 
danger of founding conclusions in Palzontology from negative 
evidence was perhaps never more strikingly illustrated than by the 
fact, that the first scientifically determined relic of a warm-blooded 
animal from that formation proved to belong to the highest order of 
that class, if man be excepted; and that besides those quadruma- 
nous remains, there have since been discovered in the London clay 
underlying the coralline crag, near Kyson, in Suffolk, teeth of cheiro- 
ptera, and of a species probably belonging to the marsupial order™. 
Mr. Owen then proceeds to describe the fossils, the immediate 
objects of the communication. 
1. The portion of the mammal was discovered by Mr. Richardson 
in the cliffs of Studd Hill, near Herne Bay, and belongs to a new 
and extinct genus of Pachydermata. It consists of a small mutilated 
cranium about the size of that of a hare, containing the molar teeth 
of the upper jaw nearly perfect, and the sockets of the canines. ‘The 
molars are seven in number on each side, and resemble more nearly 
those of the Cheropotamus} than of any other known genus of 
existing or extinct mammalia. They present three distinct modifi- 
cations of the grinding surface, and increase in complexity from 
before backwards. The first and second spurious molars have simple 
sub-compressed crowns, surmounted by a single median conical cusp, 
with a small anterior and posterior tubercle at the outer side, and a 
ridge along the inner side of its base. They are separated by an 
interspace nearly equal to the antero-posterior diameter of the first 
molar. The second and remaining molars are in close juxtaposition. 
The third and fourth molars form the principal difference between 
the dentition of the present genus and that of the Cheropotamus, 
being larger and more complex in the grinding surface. They 
present a sudden increase in size and change of form. ‘The 
plane of the crown is triangular, with the base outwards, and the 
* Annals of Natural History, Nov. 1839. ' 
> See ante, p. 1. 
