324 Principal Forms of the Dinosauria. 



Sauropoda. 



The great group which the author has called Sauropoda,. 

 and which is represented in America by at least three well- 

 marked families, appears to be rare in Europe. Nearly all the 

 remains hitherto discovered there have been found in England, 

 and most of them, in a fragmentary condition. The skull is 

 represented only by a single fragment of a lower jaw and 

 various isolated teeth, and, although numerous portions of the 

 skeleton are known, in but few cases have characteristic bones 

 of the same individual been secured. 



Quite a number of generic names have been proposed for 

 the remains found in England, and several are still in use, but 

 the absence of the skull, and the fact that most of the type 

 specimens pertain to different parts of the skeleton, render it 

 difficult, if not impossible, to determine the forms described. 



In the large collections of Sauropoda secured by the author 

 in America, which include the remains of more than one 

 hundred individuals, both the skull and skeleton are well 

 represented. On this material, his classification of three 

 families, Atlantosauridoe, Morosauridce, and Diplodocidce, has 

 been based. The PlewrocceUdce, also, appear to be distinct, 

 but the remains at present known are less numerous and char- 

 acteristic than those pertaining to the other divisions of this 

 group. 



In examining the European Sauropoda with some care, the 

 author was soon impressed by three prominent features in the 

 specimens investigated : 



(1) The apparent absence of any characteristic remains of 

 the Atlantosauridoe, which embrace the most gigantic of 

 American forms. 



(2) The comparative abundance of another family (Oetio- 

 sauridce), nearly allied to the Morosauridce, but, as a rule, less 

 specialized. 



(3) The absence, apparently, of all remains of the Diplo- 

 docidce. 



A number of isolated teeth, and a few vertebrae of one im- 

 mature individual appeared to be closely related to the Pleuro- 

 ccelidce, but this, for the present, must be left in doubt. 



Among the American forms of Sauropoda, the skull is now 

 comparatively well known in the principal families and genera. 

 Brontosaurus, Morosaurus, and Diplodocus, typical of their 

 respective families, are each represented by several skulls, some 

 of which are nearly complete, and characteristic portions are 

 known of the skulls of other genera. 



