Scientific Intelligence — Zoology. 399 



on a visit to Brooklyn, a few months since, discovered fragments of 

 these remains in the great masses of boulder-drift in South Brook- 

 lyn, through which the new streets are being excavated. At their 

 invitation, Mr Redfield had examined the place, in company with 

 Professor Agassiz, and had obtained a variety of specimens which 

 were found at depths varying from twenty-five to forty feet below 

 the original surface of the hills in which they were imbedded. 



Since that occasion, Mr Redfield has found similar remains in 

 these hills, about two miles northward from the first locality, and 

 has collected numerous specimens, which he exhibited to the meet- 

 ing, together with samples or fragments of the original beds enclos- 

 ing these shells, which had been dispersed by the drift, and thus 

 lodged in the Brooklyn Hills. The number of species comprised in 

 the collection, amounts to ten or twelve, among which are those now 

 most common to our shores. 



These discoveries, in regard to the drift, appear to agree with 

 those which Sir R. Murchison states to have been found in the drift of 

 Europe. They must be admitted as proving that the most common 

 species of our present molluscs were of prior origin to the hills where 

 the remains were found, and probably older than the entire forma- 

 tion of drift and boulders which is found in the Northern States. 

 The species obtained are not such as indicate a colder climate than 

 now prevails. But the shells found by Professor Emmons and others 

 in the pleistocene clays, on the borders of Lake Champlain, and by 

 Mr Lyell and others in Canada, appear to belong to a later period 

 of the drift ; and Mr Redfield infers that they were brought in from 

 more northern regions, or from deeper waters, by the great arctic 

 currents which must have swept over these regions during the drift 

 period, when this portion of the continent was deeply submerged. 

 These polar currents, annually freighted with immense fields Ind 

 islands of floating ice, such as are now diverted along the shores and 

 banks of Newfoundland, till they are met by the dissolving influences 

 of the Gulf Stream, nearly in the latitudes of Boston and New York, 

 he considered to be among the chief agents in producing the remarkable 

 phenomena of the drift period. — [American Journal of Science and 

 Arts, Second Series, vol. v.. No. 12, p. 110.) 



ZOOLOGY. 



10. The number of Vertebrate, Molluscous, Articulated, and Ra- 

 diated Animals. — The number of vertebrated animals may be esti- 

 mated at 20,000. About 1500 species of mammals are pretty pre- 

 cisely known, and the number may probably be carried to about 2000. 



The number of Birds well known is 4000 or 5000 species, and the 

 probable number is 6000. 



The Reptiles number about the same as the Mammals — 1500 de- 

 scribed species — and they will probably reach, the number of 2000. 



The Fishes are more numerous ; there are from 5000 to 6000 



