10 



THE AMERICAN MUSEUM JOURNAL 



From instantaneous pliotographs of the Australian water lizard (upper) and the frilled lizard (lower), 

 showing the manner in which it is believed that the small primitive, two-legged dinosaur ran. The tail 

 acts as a balancer to the fore part of the body 



consists of three digits of nearly equal 

 length, the thumb being set off from 

 the other fingers apparently for grasp- 

 ing purposes while the second and third 

 fingers are quite closely appressed side 

 by side as in the hand of the two-fin- 

 gered sloth. The terminal bones of the 

 fingers were provided with long, par- 

 tially recurved claws adapted for 

 grasping the limbs of trees, as in the 

 climbing sloths, but not adapted in any 

 way either for digging in any hard sub- 

 stance or for seizing an active prey. 

 This unique combination of characters 

 has led to a very lively discussion as to 

 the life habits of Struthiomimus. All 

 agree to abandon the idea that it was a 

 carnivorous animal, but opinion varies 

 between a purely herbivorous and a car- 

 nivorous interpretation. 



First, as to the running motions of 



the animal, it is agreed that the "os- 

 trich mimic"' is certainly the swiftest 

 reptile which has ever been discovered. 

 It nearly rivals the modern ostriches in 

 its powers of speed. As the fore part 

 of the body was balanced by a long, 

 slender, and very rigid tail, in which 

 the vertebrje are closely articulated, it 

 is apparent that it depended upon the 

 balanced mode of running, similar to 

 that which is seen in the swift bipedal 

 movements in several of the modern 

 lizards, such as the Australian water 

 lizard or the frilled lizard. The habit 

 in lizards of running upon the hind 

 legs with the body reared upward in 

 front has been observed among repre- 

 sentatives of three families — namely, 

 the Old World Agamas, and the New 

 World Iguanids, and Tegus or race 

 runners. In each of these forms the 



