Proceedings of the British Association. 343 
Vice Presidents —Rev. F. W. Hope, Dr. J. Richardson, Prof. 
Royle. 
Secretaries. —John Curtis, Esq., Prof. Don, Dr. Riley, S. Root- 
sey, Esq. 
Dr. Richardson commenced the proceedings of the Section, by 
reading the introductory portion of his report ‘“‘ On the Zoology of 
North America.”’ It did not appear probable that the progress of 
colonization had, as yet, extinguished any one species of animal 
from the country. The great similarity which existed between the 
animals of North America and those of Europe, as regarded their 
generic distinctions, connected with the dissimilarity of their species, 
rendered them well adapted to inquiries connected with their re- 
spective geographic distribution. Hitherto the trivial names be- 
stowed by the colonists upon many of those of North America, had 
tended to mislead naturalists. The observations in the present re- 
port would principally refer to the western parts of North America, 
including New Mexico, the Peninsula of Florida and California, 
down to the well defined limits of the South American zoological 
province. Dr. Richardson then proceeded to describe the physical 
structure of this country, of which the Rocky Mountains formed a 
most remarkable feature. The altitude of many of their peaks rose 
above the limits of perpetual snow, and their sides were flanked by 
zones of different temperature, affording passages for animals from 
the Arctic circle to the table lands of Mexico, without any great al- 
teration of climate throughout the whole extent. The temperate 
zones of both hemispheres might. in this way, be connected, were 
it not that the Cordilleras were greatly depressed at the Isthmus of 
Panama, and that a plain extended from sea to sea a little further to 
the south. As yet we possess no information of the elevation of the 
backs of these mountains, independent of the heights of some of the 
and the elevation of the base of the range is equally un- 
known. ‘The depths of some of the transverse valleys are consid- 
erable, and these afford passages for the migration of animals. Most 
of the principal rivers flowing to the east cut across the chain, and 
one actually rises to the west of the crests of the range. On the 
Atlantic side are prairies, composing plains gently inclining to the 
east, and there is an extent of land which may be likened to a long 
valley, which stretches from the Arctic Sea to Mexico, without any 
transverse ridges dividing it, but merely affording three distinct 
water-sheds. The greatest width of the plain is about 15° of lon- 
