8 
THE GEOLOGIST. 
be detected. Eound the back of the counterpart cavity, in the op- 
posing slab of stone, a portion of the transverse section of the back 
of the skull, showing the bony intercerebral ridge, is to be met with. 
There is near this space a conchoidal fracture, which Mr. Blake 
thinks might be the impression of the parietal and frontal bones ; but 
although we believe these bones were within the region of this space, 
we think the conchoidal fracture has been produced by artificial 
means. The proximity of these cerebral and cranial relics to one of 
the missing pieces of stone, renders it highly desirable that some 
pains should be taken to obtain it, as the beak of the bird's head 
would have probably projected upwards and inwards into it, as it 
covered the brain in the slab containing the chief remains. That is 
to say, the Archseopteryx's head would have rested on its back on 
the mud, with possibly one or two of the cervical vertebra) attached 
to it, the beak thus projecting directly upwards, exactly as we usually 
find those of dead gulls and other birds on our present shores. 
This evidence goes far to support the admirable inferences of Pro- 
fessor Owen, as the fossil brain presents true bird's characters, and 
can thus be perfectly distinguished from the very peculiar form of 
brain in reptiles. 
EXPLAKATION OF PlATE I. 
c, costae ; sc, scapula ; h, humerus ; u, ulna ; r, radius ; cr, carpals ; i, ilium ; f, femur ; 
/, tibia ; mt, metatarsus ; p, phalanges ; ca, cauda (tail) ; b, fossil brain ; a, acetabulum ; 
1 and 2, carpal hooks. 
ON DIDTMODOX,* A NEW GENUS OE MINUTE AE- 
TIODACTYLE MAMMALIA, EEOM THE EOCENE OF 
VAUCLUSE. 
By Chaeles Caetee Blake, Esq., 
Lecturer on Zoology at the London Listitutio7i. 
Since the original foundation of the genus Dichobune by Cuvier,t 
and the critical observations made thereon by Owen,J the national 
collection has continued to receive new accessions, indicating the ex- 
istence of a certain range of variation in the molars of that genus. 
The specimen (No. 30673) in the British Museum collection, is 
figured in Plate II., by Mr. Mackie. It consists of the three molars 
of the right side of a species of small quadruped closely resembling 
Dichobune. The length of the fractured ramus containing these 
teeth, of which the inner aspect is exposed to the observer, mea- 
* From UZvfios, twofold, and oSoDs, tooth. 
t 'Ossemeus Fo&siles,' vol. v., passim. 
X Quarterly Journal of the Geological Society, vol. xiii, 1857, p. 254. 
