390 T. Bland on the GeograpJiical Distribution of Molhtsca. 



in his paper on '' The results of an examination of the shells of 

 Massachusetts^ and their Geographical distributio7i,^^ read in 

 February, 1841, before the Boston Society of Natural History, 

 (published in the third volume of the Society's Journal,) and in 

 his subsequent works. — Professor Adams takes up the subject 

 in his " Second Annual Report on the Geology of the State of 

 Verinont^''^ dated October, IS 1(3, as well as in his later publi- 

 cations. 



The latter author has had the particular advantage of work- 

 ing somewhat extensively in the wide field of nature. His 

 labors in Jamaica, when confined to the terrestrial shells, re- 

 vealed to him the existence of a distinct, thongh limited zoolog- 

 ical province, and enabled him to demonstrate, that the area of 

 the marine Caribbean province, comprises several distinct terres- 

 trial insular faunas. On extending his inquiries to the marine 

 shells of the coasts of this country, of Jamaica and the neighbor- 

 ing island, and of Panama, he found means of approximately 

 defining the limits of two marine zoological provinces, viz, the 

 " Caribbean," and " Panama." An important step towards this 

 object is gained, as regards ihe latter, by the publication men- 

 tioned at the commencement of this article, and the anthor is 

 now employed, we understand, in the preparation of a more com- 

 plete work, illustrative of the former. 



We desire to shew the interest and value which are attached 

 to tlie question of the geographical distribution of shells, — not 

 only generally, as part of the animal kingdom, but in its especial 

 reference to geology. Although it may appear that much has 

 been discovered and written on the subject, it will be equally 

 apparent that very much remains to be worked out. 



We propose also to refer to the causes of error on the subject, 

 and to the question of the origin of species, which is intimately 

 connected with the fact, that different regions of the globe, both 

 of land and water, are inhabited by distinct groups of animals 

 and plants. 



It being our wish to excite increased attention to these subjects, 

 we have preferred quoting largely from works of authority, to otfer- 

 ing a summary of views and opinions in language of our own. 



Biiffon first pointed out the want of specific identity betv/een 

 the land quadrupeds of America, and those of the old world. 

 Humboldt demonstrated that zones of elevation on mountains 

 correspond to parallels of latitude, the higher with the more 

 northern or southern, as the case might be. But for a lucid and 

 succinct account of the progress and extent of our knowledge of 

 the geographical distribution of species, both of plants and ani- 

 mals, we must refer to the admirable chapters relating to it, in 

 Sir Charles Lyell's Principles of Geology. 



