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 x\merica, 

 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 

 peaks, 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 Ion- 



