5 
lies by the road-side on the north of the village of Hare Street ; and 
it is so thoroughly rounded that the author had great difficulty in 
detaching a fragment. The other boulder occurs at Baldock, and 
consists of hard chalk containing common black flints. It is about 
3 feet 9 inches high above-ground, 24 feet long, and nearly 2 feet 
broad. 
The current by which the drift was accumulated, the author con- 
ceives came from a point to the east of north, and he is of opinion 
that the materials have been derived in part from Scandinavia and 
in part from the destruction of strata, which once occupied the site 
of the German Ocean. After the deposition of the clay, Dr. Mitchell 
believes, that there was a violent action which accumulated the beds 
of gravel in some places to the depth of above 100 feet (Beaumont 
Green, 110 feet; the Isle of Dogs, 124 feet); and that this action 
will account for the clay not being found in more places, and being 
occasionally associated with beds of gravel. 
The paper concludes with a slight allusion to a similar north-east 
drift, north of the counties enumerated in the title; and it is stated 
that grey quartz boulders continue to be thrown in at Spurn Head, 
Yorkshire, similar to those which are found in some of the vales of 
the counties of Lincoln, Nottingham, and Leicester. Fragments of | 
mountain limestone, lias, oolite, grey quartz, white quartz, and hard 
chalk are said to occur about Mount Sorrell. 
Nov. 21, 1838.—A paper was first read ‘“‘ On the Jaws of the 
Thylacotherium Prevostii* (Valenciennes) from Stonesfield,” by 
Richard Owen, Esq., F.G.S., Hunterian Professor, Royal College of 
Surgeons. . 
Doubts having been recently expressed by M. de Blainvillet, from 
inspection of casts, respecting the mammiferous nature of the fossil 
jaws found at Stonesfield, and assigned to the Marsupialia by Baron 
Cuvier, Mr. Owen brought the paper before the Society, to meet the 
objections and give a detailed account of the fossils from a careful 
inspection of the originals. In this communication, however, he 
confined his description chiefly to the jaws of one of the two genera 
which have been discovered at Stonesfield, and characterized by 
having eleven molars in each ramus of the lower jaw, reserving to a 
future occasion an account of the remains of the other genust. 
Mr. Owen commences by observing that the scientific world pos- 
sesses ample experience of the truth and tact with which the illus- 
trious Cuvier formed his judgements of the affinities of an extinct 
animal from the inspection of a fossil fragment; and that it is only 
when so distinguished a comparative anatomist as M. de Blainville 
questions the determinations, that it becomes the duty of those who 
* Comptes Rendus, 1838 ; Second Semestre, No. 11, Sept. 10, p. 580. 
T Ibid., No. 8, Aout 20, p. 402 ef seq.; No. 9, Planche; No. 17, 
Oct. 22, p. 727; No. 18, Oct.:29, p. 750. - 
t See postea, p. 17. 
