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colour. The surface of some of the beds exhibits ripple-mavks. The 

 quarry, which is the property of Mr. Greer, is from 25 to 30 feet deep, 

 and the fishes are found only in the bottom beds, but are in great 

 abundance*. 



Dr. Agassiz afterwards gave a systematic enumeration of the fos- 

 sil fishes which he has found in English collections. He commenced by 

 detailing the general results of his researches, from which it appears, 

 that the discovery in England of three hundred new species has 

 corroborated the laws of development which he had previously de- 

 termined in the succession of these animals during the different 

 changes which our globe has undergone, with the exception of the 

 discovery in the chalk of two species belonging to two genera which 

 he had before observed only in the oolitic series, and of a species of 

 one of those genera in the lower tertiary strata. 



The secondary systems (^terrains) of England are the richest in fos- 

 sil fishes ; and Dr. Agassiz stated that the number of specimens which 

 he has seen in English collections is astonishing. The species which 

 he has determined are about 400 ; but the specimens too imperfect 

 to be described, at present, announce the existence of a still greater 

 number. 



Their geological distribution presents the following details: 



In the Silurian system of Mr. Murchison there are five or six spe- 

 cies which exhibit the first appearance and organization of this long 

 series of vertebral animals, the species of which become more and 

 more numerous, and more and more diversified, as well in their forms 

 as in the details of their organization. 



The old red sandstone, including the Caithness schist and the Gam- 

 rie deposit, contains twenty species. 



In the coal measures there are fifty-four species ; in the magnesian 

 limestone sixteen. 



The oolitic series is particularly rich in ichthyolites, the number of 

 species from the lias to the Wealden inclusive being one hundred 

 and fifty. 



The greensand and chalk are also very rich in fossil fishes, and 

 even much richer than their equivalents on the Continent. The num- 

 ber of English species is fifty. 



In the London clay the species perfectly determined are about fifty; 

 but it is certain, from the fragments preserved in different collections, 

 that this formation incloses the remains of a much greater number. 

 M. Agassiz stated that the London clay, particularly in Sheppey, will 

 be, for a long time, an inexhaustible mine. 



The crag contains five or six species peculiar to it, and belonging 

 to genera which do not inhabit our northern seas. 



As an example of what remains to be done in the study of fossil 

 fishes, and of the importance of these researches to zoology and geo- 

 logy, M. Agassiz afterwards described two singular genera found in 

 the lias. One is the animal which has been described under the name 



* A slab, presented to the Geological Society by Mr. Greer, exhibits, on 

 a surface not exceeding two feet square, above 250 fishes. 



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