Professor Agassiz on T aloeontology . 295 



chemistry, — and thus combined, produced, by uniting; with magnesia, 

 the mineral chondrodite, which is a compound of silica, fluorine, and 

 mao-nesia. Where spinels are not found, as with rare exceptions is 

 the^case in St Lawrence county, New York, it may be owing to the 

 large amount of silica present, or the absence of fluorine. Chondro- 

 dite is nearly as rare a mineral in Northern New York as spinel. 



Remarks on Professor Pictefs Treatise on Palasontology . By 

 Professor Agassiz. 



The publication of a general work on Palaeontology by an 

 entomologist,* is calculated to excite our surprise, especially 

 when, as is the case with our author, that entomologist occu- 

 pies a place in the first rank, both on account of his learning 

 and his writings. Entomology is indeed the most exclusive 

 of all the branches of natural history ; and it has always been 

 a matter of remark, that the naturalists who have devoted 

 themselves to the study of articulated animals neglect more or 

 less the other divisions of the animal kingdom. Latreille him- 

 self has not succeeded in fixing the attention of the learned 

 on those of his works which do not treat directly of ento- 

 mology. This isolation is undoubtedly to be regretted ; but it 

 is rendered intelligible if we reflect that the prodigious num- 

 ber of insects, the variety of their metamorphoses, and the 

 very marked peculiarities of their organization, demand the 

 whole attention of those who attempt to advance this depart- 

 ment of science. Thus, if I had to analyze an entomological 

 work of M. J. Pictet, in order to recommend it to the atten- 

 tion of the scientific world, I would content myself with stat- 

 ing that it was the production of the same pen which had 

 given us the " Becherclies pour servir d t Histoire et d V Ana- 

 tomie des Pliryganldesr and the " Histoire Naturclle des In- 

 sectes Neuroptcres.'" But M. Pictet has entered a new arena. 

 Under the title of " Trait'e elemenlaire de Paleontologie on HiS' 

 toire Nalurelle des Animaux Fossiles,^^ he has just published the 



* TraUe EUmentaire de Paliontologic ou Histoire Naturclle des Animavx 

 Fossilei comidiris dans levrs rapports Zoolofjiques et Gcologiqvcs, Par F. J. 

 Pictet, Professeur de Zoologie et d'Anatomie Cotnparee a TAcademio 

 de Geneve. 



