1 6 OLIVER P. HAY 



ii, 1883, p. 117, pi. iii, fig. 8) as the tracks of Igiianodon mnntelli. A 

 study of these footprints shows that in the case of the series designated 

 by cc the length of the step was close to 5 feet while the width of the 

 trackway was about 2 feet 2 inches. The tips of the inner toes came, 

 however, pretty close to the line of direction. It must be observed that 

 in all of these tracks the toes are turned inward so much that the axis 

 of the middle toe prolonged passes through the next imprint in front, 

 made by the opposite foot. Now, I find no reason for supposing 

 that in life the toes were so directed inward. None of the figures of 

 Iguanodon so represent them; nor are the toes thus placed in any of 

 the restorations of Tracliodon. The explanation of the matter seems 

 to be that the reptile, if reptile it was, was lounging leisurely along, with 

 short steps, and, to keep its equilibrium, was swinging its body around 

 a perpendicular axis passing through the pelvis, the tail being thrown 

 in one direction, the trunk in the opposite. In this way the feet would 

 be planted not far from the line of direction and pointing toward it. 

 Had the animal been running, the feet would have been planted 

 farther from the line of direction and with toes directed forward. 



Now, if these conclusions regarding the gait of the Upper Jurassic 

 and Upper Cretaceous carnivorous dinosaurs are justified, is it prob- 

 able that the Triassic Anchisaurus colurus, with an equally hea\y 

 abdomen and with less elongated and more primitive limbs, had the 

 ability to walk, just as a bird does, accurately placing one foot directly 

 in front of the other and under the center of gravity? It seems to 

 the writer that we need more proof of it. If it could so walk, one 

 might inquire what was the useof all the modifications undergone by the 

 dinosaurs up to the end of the Cretaceous. It seems most probable 

 that Anchisaurus walked usually in crocodilian or lacertilian style, 

 with, however, the femora drawn somewhat more closely to the sides. 

 Now and then, when in great haste and for short distances, it was 

 probably able to progress bipedally in an awkward fashion. In the 

 same category may be placed some of the European dinosaurs figured 

 by Dr. v. Huene, such as Thecodontosaurus anliquus and the species 

 of Plateosaurus. Others, as Pachysaurus ajax and Massosaurus 

 carinaius, probably walked more or less habitually on their hinder 

 limbs, but with a wide trackway and with much swinging of the tail 

 from side to side. 



Dr. v. Huene's statement of his view of the manner of insertion of 



