Association of American Geologists and Naturalists. 99 



Prof. Haldeman read a paper — " Enumeration of the recent 

 Fresh- Water MoUusca which are common to North America and 

 Europe, with observations on species and their distribution." 



Eight fresh-water species are enumerated as common to the two sides 

 of the Atlantic ; but as some naturahsts doubt the identity of species 

 found under such circumstances, a portion of the paper is devoted to an 

 attempt to prove that the same species can occur in the most distant 

 locabties, whether by transportation, former connexion of the regions, 

 distribution from more than one original centre, or by transmutation of 

 species. The two first are the most obvious, whilst the probabilities 

 against the third are stated to be not less than as ten thousand to one. 

 The Lamarkian hypothesis of transmutation is reviewed at some length, 

 and the fallacy of many of the arguments brought against it by Mr. Lyell 

 and others pointed out. 



For reasons given in the article, the Physadce alone are taken for 

 the determination of the per centage of fresh-water shells common to 

 the two continents, and of these the proportion assigned is five per cent., 

 a proportion which is stated to obtain in the Brachelytra, a division of 

 insects. 



No opinion is offered for or against the theory of transmutation, this 

 being considered an open question, and one which has but a slight bear- 

 ing upon geology ; because, were species transmutable, it would be 

 during the course of the geological periods, and that, whether organic 

 remains be assumed as at one time identical with recent species, but 

 now distinct, or as distinct at all times, the result and its applications to 

 geology must be the same. 



A number of authorities are cited to prove that the same animals, in 

 a number of instances, are found to inhabit distinct regions ; some phy- 

 siological points are discussed, and solutions offered to several imagin- 

 ary problems which have a bearing upon the subject. 



After a recess, the Hon. Nathan Appleton presented from 

 George Ticknor, Esq. of Boston, a letter from Baron Yi. Sarto- 

 rius Yon Waltershausen, dated Gottingen, December 18, 1843, 

 describing his great work, called "iEtna and its Convulsions," 

 upon which he has been occupied for seven years, and which 

 will be published in the next six years, one portion each year. 

 The work will be illustrated by a book of plates, containing fifty 

 four large engravings, (beautiful specimens of which were also 

 presented,) to appear in six numbers ; a topographical map in fif- 

 teen sheets, on a scale of 1 to 50,000, and a geological map in 

 fifteen sheets, with views, sections, and other drawings. 



