JURASSIC VERTEBRATE FOSSILS. 483 



and forward. The distal ends are closely applied to each other, but not 

 materially expanded, and in the present specimen are not coossified with 

 each other. The ischia projected downward and backward, and their distal 



extremities are expanded, somewhat as in the Crocodilia. 



The femur is comparatively short, with the shaft curved and very 

 hollow. The tibia is nearly straight, much longer than the femur, and its 

 shaft equally hollow. The fibula was slender and complete, but tapered 

 much from above downward. Its position below was not in front of the 

 tibia, -as in all known dinosaurs, but its lower extremity was outside, and 

 apparently somewhat behind, the tibia. 



The astragalus is large, and covered the entire end of the tibia, but 

 was not coossified with it. The calcaneum is compressed transversely, and 

 much produced backward. It was closely applied to the outside of the 

 astragalus, and although agreeing in general form with that of a crocodile, 

 strongly resembles the corresponding bone in some mammals. 1 Tie tarsal 

 joint was below the astragalus and calcaneum. There appears to be but a 

 single bone in the second tarsal row, although this nun' be composed of 

 two or more elements. j 



There were but three functional digits in the hind foot, and their 

 metatarsals are greatly elongated. The first digit seems to be wanting, 

 and the fifth is represented only by a remnant of the metatarsal. The 

 posterior limbs, as a whole, were especially adapted for leaping, and are 

 more slender than in almost any other known reptile. 



There are but two vertebras in the sacrum. The other vertebra' 

 preserved have their articular faces biconcave. The chevrons are slender 

 and very elongate. 



This interesting reptile was found near Canyon, in the horizon that 

 now hears its generic name. No other specimen is known. 



NANOSAURI S. 



In the same geological horizon in which the type of Hallopus was 

 found, but at a different locality in the same vicinity, the skeleton of 

 another dinosaur was discovered, still more diminutive, and indeed the 

 smallest known member of the group. The remains are well preserved, 



