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COLOSSOCHELYS ATLAS. 373 



specimens of huge fragments derived from all parts of the 

 skeleton of the Colossochelys. 



Dr. Falconer commenced with a reference to the history 

 of the reptilian forms discovered in the fossil state (chiefly 

 in the older strata, such as the lias and oolite), among which 

 colossal representatives have been found of almost all the 

 known tribes, such as the Megalosaiirus, Iguanodon, &c., 

 besides numerous remarkable forms of which no analoo-ues 

 are now m existence, such as the Ichthyosaurus, Plesiosaurus, 

 and Pterodactylus. Even the Batrachian order, or Progs, was 

 represented in the fossil state by the gigantic Labyrinthodon 

 of Professor Owen. But no fossil Testudinata, remarkable 

 either for size or deviation from existing forms, had hitherto 

 been met with. The existing species of sea-tui-tle were 

 larger than any which had been found of the order in the 

 fossil state, and the most remarkably modified known form 

 was an existing species, the Chelys Matamata. Nature, 

 however, consistent in her course, had not left the Chelonian 

 order without a grant. The Golossozlelys fills up the appa- 

 rent blank, and yet differs so little from the ordinary land- 

 tortoise, in the general construction of its osseous frame, as 

 hardly to constitute more than a sub-genus of Testudo, whUe 

 at the same time it furnishes one of the most gigantic forms 

 found in any section of the reptilian order. 



The anatomical structure was then briefly described. The 

 plastron or sternal portion of the shell affords the chief dis- 

 tinctive character, and the elements for determining the size, 

 form, and affinities of the fossil. Dr. Falconer explained 

 that the diagram was not drawn from any one entire speci- 

 men of the shell and skeleton, of which there was probablj' 

 none in existence either above or below ground, but that it 

 was what is called a Cuvierian restoration founded on the laws 

 of relation between special and general structure ; in fact a 

 reconstruction of the form determined upon the collation 

 of a vast number of specimens of the individual parts. 

 Allusion was here made to the laws of reciprocal connection 

 between special and general structure, which involves the 

 necessary condition that every individual part has a definite 

 relation to the aggregate form, and to every other part of it ; 

 or, to express the law in mathematical language, that each 

 proportion of an animal is a function of every other propor- 

 tion and of the sum of those proportions. The application 

 of this law to the reconstruction of the Colossochelys was 

 next considered, and it was shown how far the sternum, 

 carapace, extremities, and head had common tendencies, 

 land how far they warranted the size, form, and generic 

 .representation in the figure. The anatomy of the Colosso- 



