SOS AFFINITIES OF EXTINCT SPECIES. Cii.vp. X. 



Another distinguished paleontologist, M. Gaudry, shows, in 

 the most striking manner, that very many of the fossil mam- 

 mals discDvered by him in Attica, connect in the plainest man- 

 ner existing genera. AMiat a -wonderful intermediate form is 

 the Tyiiotherium from South America, as the name given to it 

 by Prof. Gervais expresses, and Avliich cannot be placed in any 

 existing order of mammals ! Even the wide interval between 

 lairds and reptiles has been shown by Prof. Huxley to be par- 

 tially bridged over in the most unexpected manner, by, on the 

 one hand, the ostrich and extinct Archeopteryx ; and, on the 

 other hand, the Compsognathus, one of the Dinosaurians — that 

 group which includes the most gigantic of all terrestrial rep- 

 tiles. Turning to the Invertebrata, Barrande asserts, and a 

 higher authority could not be named, that he is every day 

 taught that, although paleozoic animals can certainly be classed 

 under existing groups, yet that at this ancient period the 

 groups were not so distinctly separated from each other as they 

 now are. 



Some writers have objected to an}' extinct species or group 

 of species being considered as intermediate between living 

 species or groups. If by this term it is meant that an extinct 

 form is directly intermediate in all its characters between two 

 living forms, the objection is valid. But in a natural classifi- 

 cation many fossil species certainly stand between living spe- 

 cies, and some extinct genera between living genera, even 

 between genera belonging to distinct families. The most 

 common case, especially with respect to very distinct groups, 

 such as fish and reptiles, seems to be, that, supposing them to 

 be distinguished at the present day by a dozen characters, the 

 ancient members are separated by a somewhat lesser number 

 of characters, so that the two groups, though formerly quite 

 distinct, made at that period a somewhat nearer approach to 

 each other. 



It is a common belief that the more ancient a form is, by 

 so much the more it tends to connect by some of its characters 

 groups now widely separated from each other. This remark 

 no doubt must be restricted to those groups Avhich have mider- 

 gone much change in the course of geological ages ; and it 

 would be difficult to prove the truth of the proposition, for 

 every now and then even a living animal, as the Lepidosiren, 

 is discovered having affinities directed toward very distinct 

 groups. Yet if we compare the older Reptiles and Batra- 

 chians, the older Fish, the older Cephalopods, and the eocene 



