300 Miscellaneous. 
Most of the species on the east coast appear to be common to Europe, those on 
the west are also found in Asia. About nine in all have been described as North 
American. 
AVES. Dr Richardson professed not to enter very fully into details respecting 
the different orders of birds, as the species were generally much more known than 
those of the Mammalia. Many of them being migratory, quitted the less acces- 
sible countries at stated periods of the year, and in passing through those tracts 
which were comparatively civilized, afforded the naturalist an opportunity of 
studying their habits. Their geographical distribution was still very imperfect- 
ly known, from the want of local lists, more especially in California and Rus- 
sian America. About 500 species were now described, nearly one-fourth of 
which were common to Europe, and about one-eighth to South America. Of 
those common to North America and Europe, there were 39 land-birds, 28 wa- 
ders, and 62 water-fowl. Several genera were confined to North America, but 
only two families, the Trochilidas and Psittacidae, were absent from Europe. 
The birds of prey in general have an extensive range, some of the North Ame- 
rican species being found in the most distant parts of the world, others extend 
through South America, nearly half of them are common to Europe, if we ex- 
cept the vultures, of which those in the new world are peculiar to that country. 
Except the Corvidae, of which one-fourth are also common to Europe, the rest 
of the North American land birds are for the most part restricted to that coun- 
try, and two only out of the 62 Sylviadae are found in Europe. Twenty-two 
species of Trochilus are described as natives of Mexico, but not one of the North 
American species has been met with in South America, although the family to 
which they belong is peculiarly characteristic of the ornithology of that country. 
In accounting for the causes which determined the migration of North American 
birds, Dr Richardson considered the spring movement intended for the purpose 
of finding suitable spots for breeding. The chief lines of route, he described as 
being mainly determined by the greater or less facility experienced in procuring 
food, from which circumstance the flights northwards and southwards often ex- 
tended over very different lines of country.. The physical structure of North 
America was also effective in determining three particular courses, along which 
these migrations occurred. The progress of civilization has already produced a 
decided effect in the migrations of some species, causing the starlings, for in- 
stance, to proceed further northward, as they are now secure of finding a provi- 
sion in the corn-fields, where formerly they would have obtained no food. A 
table was then explained, in which were exhibited the total number of species 
hitherto known, with references to those which breed in Philadelphia, Massa- 
chusetts, and Suskatchewan. He considered America to afford remarkable fa- 
cilities for tracing the course of the different tribes in their migrations, and con- 
cluded his report by a notice of certain desiderata to our knowledge of North 
American zoology, which will be printed apart in the forthcoming volume of the 
Reports of the Association. 
Mr Rootsey exhibited a living specimen of a large spider, which had been ac- 
cidentally imported in a freight of logwood from the Bay of Campeachy. He 
supposed it to be the Aranea avicularia, Linn. Mygale avicularia of modern au- 
thors. But Mr Hope expressed his opinion that it was not this insect, but a 
closely allied species described by Spix and Martins. He stated, however, that 
