68 Zoological Society. 
Mr. Owen concludes it was not provided with poisonous fangs. 
Serpents of similar dimensions exist in the present day only in 
tropical regions, and their food consists principally of the warm- 
blooded animals. Mr. Owen therefore in conclusion states, that had 
no evidence been obtained of birds or mammals in the London clay, 
he would have felt persuaded that they must have coexisted with 
the Paleophis Toliapicus. 
ZOOLOGICAL SOCIETY. 
December 10, 1839.—William H. Lloyd, Esq., in the Chair. 
A letter from Dr. Weissenborn, dated Weimar, October 6, 1839, 
was read. It accompanied a present of two specimens (male and 
female) of the black variety of the common Hamster (Cricetus vul- 
garis), and a head, preserved so as to display the cheek-pouches of 
that animal. The writer of the letter states that he possesses a 
common Pigeon, just fledged, in which no vestiges of the organs of 
vision can be traced. ‘‘'The orbits are tolerably well developed, and 
lined with a sort of half-mucous membrane, and therefore destitute 
of feathers. I have never heard of a similar defect in any animal; 
and in one where the incubation is extra-uterine it appears doubly 
wonderful or anomalous. ‘The bird is quite healthy, and presents in 
its habits several curious anomalies, which may be traced to its mon- 
strosity.”” 
Professor Owen communicated his notes on the Anatomy of the 
Biscacha (Lagostomus trichodactylus, Brookes). 
« The individual dissected,” says Mr. Owen, “‘ was a female, full- 
grown, weighing 8 pounds 2 ounces, avoirdupois : the weight of the 
brain was 5 drachms, avoirdupois, the proportion of the brain to the 
body being as 1 to 416. This is the smallest relative size of the 
brain that has yet been recorded in the Rodent order, in some of the 
species of which order, as the Mouse, the brain approaches that of 
Man, the relation of its mass to that of the body being as 1 to 46; 
that of the human subject is as 1 to 30. . The brain presented the 
usual broad depressed form and simple unconvoluted surface charac- 
teristic of the Rodent order : its length was 1 inch 8 lines, its breadth 
1 inch 5 lines, and the length of the cerebral portion 1 inch 3 lines. 
The proportion of the cerebellum to the cerebrum was as | to 5. 
The breadth of the medulla oblongata was to that of the cerebrum as 
1 to 6.. The upper surface of each lobe of the cerebrum is marked 
with two slightly curved fissures, each between 3 and 4 lines in 
length, and one a little in advance of, and exterior to the other: a 
single anfractuosity defines the external convex prominence of the 
cerebrum. On the under surface a fissure is continued from the 
posterior part of the cerebral hemisphere forwards, along the middle 
of the natiform protuberance, to the outer boundary of the root of 
the large olfactory nerve. 
“On laying open the abdomen an immense accumulation of adi- 
pose membrane concealed the viscera; the bag of the great omentum 
