Association of American Geologists and Katuralisls. 147 



tries ; and those species which now appear identical will, the Pro- 

 fessor thinks, one day be determined to be unlike in their structure and 

 character. One of the grand results shewn by the naturalists of the 

 Exploring Expedition is, that the land-shells of the islands in the 

 Pacific Ocean are entirely different in different islands ; each island 

 appears to have a species of shell peculiar to its own formation. These 

 shells could not have been derived from the continent, but must have 

 orioinated on the respective islands where they are found. The 

 geographical distribution is connected with the features of a country ; 

 as, for instance, the monkey tribe is confined to the tropics. The 

 fossils of New IloUand and of Brazil belong to the same families of 

 animals that now inhabit these countries ; this fact shewing that the 

 same laws prevailed before man had anything to do with the geogra- 

 phical distribution of animals, as prevail at the present time. The 

 geocrraphical distribution indicates the primitive origin. The higher 

 organised beings are found in the higher climates ; the lower orga- 

 nization in colder climates. The Alligator, the highest organization 

 of the reptile family, is found alone in the tropics. Frogs exist only 

 in cold regions, and so of other animals and reptiles. The monkey, 

 which possesses of all other animals the strongest affinities to man, 

 is confined to the tropics. As the new species of the monkey tribe, 

 which had been described by Dr Wyman, lives in the land of the 

 Negroes; and as they claim affinity to it, Professor Agassiz was in- 

 clined to think that the negro has a more intimate connection with 

 the country where he lives than is generally admitted. The fact 

 that the lowest terrestrial mammalia (the Pachydermata) are found 

 in the tropics, may seem to contradict the position that the nearer 

 the approach to the higher regions, the higher the organization. 

 But these mammalia are the remnants of ancient races of animals. 

 The shells and fishes of the shores of Massachusetts have been treated 

 in an able manner by Drs Gould and Storer. But the Radiated ani- 

 mals and the Crustacea have been almost entirely neglected. The 

 latitude in which an animal is found must not only be considered, 

 but also the depth of water at which it lives ; and this because the 

 conditions of existence are different at different depths. The same 

 species do not live in shallow and deep water. A very iew feet be- 

 low low-water mark the species differ greatly from those above it. 

 And this small difference between low and high water mark cox-re- 

 sponds to several thousand feet in height in the diffusion of terrestrial 

 animals above the level of the sea. The types also vary as you 

 descend down to the depth of eight or nine fathoms ; so that there 

 are as it were levels, where the animals found in the separate levels 

 difler cntiix-ly from those in the levels immediately above and below. 

 The Professor thought it singular that the different depths at which 

 various kinds of fish are caught, had never called the attention of 

 naturalists to the habits, &c. of the lower class of animals inhabiting 

 the water at different levels of the ocean. 



Professor Adams mentioned the existence of a singular pond on 



