Vi a aoe ea a 
AP RE NDA. 
Art. LUI—Principal Characters of American Jurassic 
Dinosaurs; by O.C. Marsu. Part V. With seven Plates. 
In previous articles, the writer has described the main 
characters of Morosaurus, Apatosaurus, Diplodocus, and 
Atlantosaurus, the best known genera of the Sawropoda 
ti 
second species, equally gigantic in size, has since been found, 
and its distinguishing features are also here recorded. 
-wo new genera from the same formation are noticed, and an 
outline of classification of the best known American Jurassic 
Dinosaurs is proposed. 
Brontosaurus excelsus Marsh.t 
The present genus may readily be distinguished from all the 
other | oda by the sacrum, which is composed of fiv 
ankylosed vertebrae, none of the other genera in this group 
having more than four. The sternum, moreover, consists of 
two separate bones, which are parial, and were united to each 
other on the median line apparently by cartilage only. In 
many other respects the genus resembles Morosaurus. 
the present species, aside from its immense size, is distin- 
guished by the peculiar lightness of its vertebral column, the 
cervical, dorsal, and sacral vertebree all having very large cavi- 
ties in their centra. The first three caudals, also, are lightened 
by excavations in their sides, a feature not before seen in this 
group, and one not shared by the other species of this genus. 
* This Journal, xvi, 411, Nov., 1878, and xvii, 86, Jan., 1879. 
t This Journal, xviii, 503, Dec., 1879, and xix, 395, May, 1880. 
