240 LOUIS AGASSIZ. 



modest resources were not sufficient to continue the work, as it was ac- 

 companied by expensive plates.* The Geological Society of London, 

 aided by Lord Enniskillen and Sir Francis Egerton, furnished the means 

 he lacked. A draftsman, Denkel, worked for him constantly for sev- 

 eral years. This publication, which may be regarded as a continuation 

 of Cuvier's Eesearches upon fossil bones, was not finished until 1843. 

 It is the most original work of Agassiz, and one of the principal monu- 

 ments of his greatness. 



There is no class of animals that can furnish elements more imi^ortant 

 for the history of the development of the organic kingdom, the law of 

 the succession of beings, and the relations of the fossil fauna than the 

 fishes. They alone of the vertebrates appeared in the first ages of the 

 world, and passed through all the phases of creation up to the present 

 time. 



An osteology of fishes, a rational classification, the description of a 

 multitude of new species, and theoretic consequences of great imijort- 

 ance were the results of the wise researches of Agassiz. 



One of the distinctive characteristics of this class of animals is a skin 

 covered with scales of peculiar form and structure ; now the nature of 

 this envelope is in direct accordance with the interior organization. 

 The scales, therefore, from this point of view, are of great importance, 

 and may serve as a basis of classification. The author subdivides them 

 into four orders, as follows : 



Cycloids. — Scales imbricated, corneous, and without enamel, the pos- 

 terior edge simple. Skeleton bony. 



Ctenoids. — Scales imbricated, corneous, without enamel, the i^osterior 

 edge indented. Skeleton bony. 



Ganoids. — Scales angular, and covered with a layer of enamel, their 

 edges uniting regularly. Skeleton less bony than the preceding, some- 

 times cartilaginous. 



Flacpids. — Osseous plates, disposed irregularly, terminated on the 

 upper side by points or hooks. Skeleton cartilaginous. 



The last two orders have existed from the first appearance of life ui)on 

 the surface of the globe. The others commenced with the Cretaceous 

 period, and include most of the fishes of the present time. This classifi- 

 cation has since undergone important modifications; it however assisted 

 very considerably progress in the knowledge of this class. The hand 

 of genius, said Pictet, is everywhere manifest throughout this beautiful 

 work. 



The monograph of the fishes of the old red sandstone, undertaken at 

 the request of the British Association for the Ad^'ancement of Science, 

 and completed in 1844, sui)plemented the i)rcceding work.t The author 



* Eecherchcs sur Jes Poissons fossiles ; 5 volumes quarto, with au atlas of 384 plates, in 

 folio, most of the figures beiug colored. 



\ SupxMment mix rechci sites sin- les Poissons fossiles. Monograpliie des poissons fossiles 

 du vieux gres rouge ou systeme devonxen des ilea Britanniquea et de Eiissie. 4to. 41 x>l. 

 1844-1845. ^^ 



