16 The Life and Writings of Agassiz. 



nodermesy This number contained the monograph of the 

 SalenicB, small Echini belonging to the chalk. It was follow- 

 ed by three others, treating of the Scutellm, the Galerites, 

 and the anatomy of the Echinus, — the last number edited by 

 M. Valentin. To facilitate the study of these curious ani- 

 mals, so important to the history of successive creations, 

 Agassiz made casts in plaster of all the specimens in his 

 possession. This collection comprises casts of nearly five 

 hundred species, the counterparts of which are to be found 

 in the great museums in Europe, and has thus become one 

 of the most precious documents we possess concerning this 

 class of animals. 



The labours of M. Agassiz on Fossil Shells are not less 

 important. A young Swiss geologist, M. Grossly, had made 

 a considerable collection of fossil shells from all the stages 

 of the oolitic and cretaceous formations. M. Agassiz com- 

 menced the publication of them in a work, entitled '* Etudes 

 Critiques sur les Mollusques FossUes du Jura et de la Craie.^' 

 Of this, four numbers have appeared, with a hundred quarto 

 plates, comprising the group of the Trygonice, and that of the 

 Myw. At the same time Agassiz published a German trans- 

 lation of Buckland's Geology, with numerous notes and addi- 

 tions, and revised the French and German translations of 

 Sowerby's Mineral Conchology. 



But whatever may be any man's ability and energy, na- 

 ture has fixed certain limits to what it is possible for him to 

 accomplish, which he cannot pass. Thus, in order to explain 

 the rapid succession, at so short intervals, of the works we 

 have mentioned, and those of which we have yet to speak, 

 we must observe, that about this time (1837), Agassiz asso- 

 ciated with himself a young naturalist, M. Desor, — who has 

 ever since laboured with him and under his direction, and 

 who having accompanied him in all his alpine excursions, 

 and in his visit to this country, is now living among us. To 

 the information personally furnished by M. Desor, as well 

 as to his writings, we are indebted for much of the present 

 sketch, which would not have been written without his assist- 

 ance. 



The united labours of the two friends accomplished what 



