499 O. C. Marsh—American Jurassic Dinosaurs. 
Hallopus, gen. nov. 
nus to which it was referred, and presents some peculiar 
characters. Some of these characters are as follows: 
(1) There are but two vertebree in the sacrum. 
(2) The femur is shorter than the tibia. 
(3) The metatarsals are one-half the length of the tibia. 
tay The calcaneum is much produced backward. 
this classification may appropriately be presented in the present 
article. Most of the many genera and species represented in 
this series can be readily grouped in five suborders, as given 
* This Journal, xiv, 255, Sept. 1877. 
