242 LOUIS AGASSIZ. [CHAP. x. 



work, which is composed of four octavo volumes, con- 

 taining the literature of zoology and geology until 1846; 

 a most useful publication, dated London, 1848-1854. 



In 1845 another memoir on fossil conchology was 

 published by Agassiz, under the title : " Iconographie 

 des coquilles tertiaires reputees identiques avec les 

 especes vivantes ou dans differents terrains de 1'epoque 

 tertiaires, accompagnee de la description des especes 

 nouvelles," in " Nouveaux Memoires de la Societe Helve- 

 tique des Sciences Naturelles," Vol. VII. It is, perhaps, 

 the most objectionable paper he ever produced. Start- 

 ing from a preconceived idea that not a single animal 

 survived a geological epoch, and that no species passed 

 from one formation to another, with his great faculty 

 for differentiating specimens, he easily pointed out a 

 certain number of cases of Lncina, Venus, Cytherca, 

 Cyprina, and other acephales, which showed variations, 

 and which, according to his views, demonstrated that 

 the species, instead of being identical, were only analo- 

 gous. Deshayes and other conchologists did not accept 

 Agassiz's view, and, in fact, later knowledge has greatly 

 added to the number of species which pass from one 

 formation to another, not only for the tertiary epochs, 

 but also for the Mesozoic and the Paleozoic forma- 

 tions. The complete destruction of faunas and creation 

 of new and entirely different ones, without the survival 

 of a single species, can no longer be defended ; more 

 especially in its application to marine animals. As 

 usual, the memoir of Agassiz is beautifully illustrated 

 with fourteen plates, representing with great care all 

 the details of the shells. 



