R. S. Lull — Dinosaur dan Distribution. 7 



" To the present writer [Hay] the suggestion of Dr. Holland 

 has in it more of probability than any of the others presented. 

 If the food-plants sought by Diplodocus had been large and 

 such as required uprooting by the great claws of the reptile, 

 the prehension and manipulation of the masses would have 

 been liable to break the slender teeth and would certainly have 

 produced on them perceptible wear. * * * 



"It is more probable that the food consisted of floating algae 

 than of plants that were loosely attached to the bottoms of 

 stagnant bayous and ponds. ... In addition to various algae 

 were probably other floating plants." 



The teeth of the Sauropoda, notably Morosaurus and Apto- 

 saurus (Brontosaurus), are much more robust and frequently 

 show decided wear. This wear, however, is along the edges 

 on either side of and sometimes including the apex ; which 

 could readily be accounted for by abrasion of the alternating 

 teeth of the opposing jaw and which could not be due to 

 scraping of vegetation from the rocks. The food of these 

 animals may have been more in keeping with the character of 

 that mentioned by Osborn. 



It is interesting to note in this connection, a propos of the 

 question of the digestibility of huge masses of unmasticated 

 vegetation, the occurrence of "stomach stones" or "gastroliths" 

 (Wieland 1906) which seem to have had an important 

 function in aiding in the trituration of the food. Wieland 

 records the occurrence of such polished flint pebbles in immedi- 

 ate association with the remains of a large sauropod observed 

 at the northern end of the Big Horn Mountains. Pebbles, 

 presumably gastroliths, were also found by Wieland with the 

 type of the Sauropod genus Barosaurus from near Piedmont, 

 South Dakota. 



Dr. Hay (loc. cit., p. 673-674) further says : "Hatcher has 

 discussed at length the nature of the region in which the 

 species of Diplodocus and their allies lived, as well as the 

 habits of the Sauropoda in general ; and the present writer 

 [Hay] agrees with him on most points. Hatcher believed that 

 the Atlantosaurus [Morrison] beds were deposited, not in an 

 immense freshwater lake, as held by some geologists, but over 

 a comparatively low and level plain which was occupied by 

 perhaps small lakes connected by an interlacing system of 

 river channels. The climate was warm and the region was 

 overspread by luxuriant forests and broad savannas. The 

 area thus occupied included large parts of the present 

 states of Colorado, New Mexico, Utah, Montana and the 

 Dakotas. In his memoir on Diplodocus Hatcher compares 

 the conditions prevailing in that region during the Upper 

 Jurassic [Lower Cretaceous] to those now found about the 



