8 R. 8. Lull — Dinosaurian Distribution. 



month of the Amazon and over some of the more elevated 

 plains of Western Brazil. 



"In such regions the rivers, fed from distant elevated lands, 

 must have been subject to frequent inundations. The beds of 

 the streams were continually shifting, and there existed 

 numerous abandoned channels that were tilled with stagnant 

 water. An animal that lived in such a region would be com- 

 pelled to adapt itself to a more or less aquatic life, and this 

 adaptation would be reflected to a greater or less extent in 

 the structure of the animal." 



Through the courtesy of Dr. Holland, I have been able to 

 study somewhat critically an undoubted sauropod footprint 

 from the Morrison dinosaur quarry at Canon City, Colorado. 

 Hatcher figures a cast of this track in his memoir on the 

 osteology of Haplocanthosaurus (1903, fig. 23, p. 161). The 

 figure is somewhat deceptive, however, in that it was taken 

 from a plaster cast of the specimen which in turn is a natural 

 cast of the original impression made by the living animal and 

 which is therefore in relief. The surface of the specimen 

 itself is covered with deep pits caused by a solution of the 

 calcareous cement which bound the grains of sand together, 

 thus allowing the latter to be washed out. In the photograph 

 the casts of these pits, being in relief, give the impression of 

 pebbles, whereas the rock in the quarry is a fine-grained, cross- 

 bedded sandstone of uniform texture, without appreciable clay, 

 and not gravelly at all. A microscopic study of the sand- 

 grains themselves show them to be angular with slightly 

 abraded corners, sand of aqueous deposit ; but apparently laid 

 down in a lake or bayou, rather than in a normal river as 

 indicated by the absence of clay and the presence of a lime 

 cement. The cross-bedding which the rock exhibits could 

 readily have been made by wave action along the shores of a 

 comparatively shallow delta-lake or bay, and the track, which 

 is that of a very young animal, was evidently made under 

 water. The character of the sediment does not give evidence 

 of much vegetable matter at the particular point where the 

 track was made. The footprint is that which one would 

 expect from the known character of the sauropod foot, and is 

 evenly impressed throughout as though the animal's weight 

 were borne equally over the entire sole, evidence in favor of a 

 true walk rather than a sprawling crawl, at any rate when the 

 body was partly water-borne. 



I believe these animals to have been truly aquatic though 

 capable of coming ashore where the substratum was sufficiently 

 firm to support the immense weight, and, while they show no 

 trace of swimming appendages, they doubtless could swim as a 

 hippopotamus does or, as Hay (1908, p. 667) has implied, like a 



