E. S. Lull — Life of the Connecticut Trias. 405 



compact type of foot, long stride, sometimes suddenly lengthen- 

 ing marvellously, and the narrow trackway of many species, it 

 can easily be seen that the character imposed by the desert of 

 speed and great travelling powers was here at a high premium. 

 As I have shown elsewhere (1910, p. 37), a climate of semi- 

 aridity, compelling cursorial adaptation as a means of getting 

 food but more especially water, may w r ell have been an impel- 

 ling cause in dinosaurian evolution. Bipedality among lizards 

 of to-day is, so far as I am aware, confined to denizens of semi- 

 desert environment, certain instances being the large frilled 

 lizard, Chlamydosaurus (Sayville Kent), of Australia, and 

 several lacertilian species of our own Southwest. 



That water was rare and at a premium when the rains did 

 come is evidenced by the frequency of the association of rain- 

 prints with dinosaurian tracks and the above-mentioned mud- 

 cracks which followed the passage of the animal. Again, the 

 depth of the impression of the tracks of two species of animals 

 upon the same strata is sometimes entirely out of proportion to 

 the apparent difference in the makers' size, for the presump- 

 tion is that then as now the supporting area of an animal's 

 feet must have borne a certain ratio to the weight in accord- 

 ance with the type of environment to which the creature was 

 adapted. The inference is, therefore, that the passage of the 

 two animals was on their way to or from a water hole during a 

 period of desiccation, and that the deeper impression was made 

 some time before the shallower one and nearer the time of the 

 preceding rains. 



The Vegetal Environment. 



Chamberlin and Salisbury (Vol. iii, pp. 38-40) speak thus 

 of the plant life of the Triassic : 



"The record of the vegetation is very imperfect. The 

 vegetation was probably scanty in reality, for . . . arid 

 tracts imply conditions inhospitable to plant life. An environ- 

 ment that could give rise so generally to coarse red sandstones 

 and conglomerates — even limestone conglomerates — could not 

 well be congenial to luxuriant vegetation. 



" The Triassic was distinctly an age of gymnosperms the 

 world over ; the supremacy of the pteridophytes had ceased, 

 though ferns, true to their persistent nature, still held an 

 important place, and the equisetales were a more vital factor 

 than now. . . . conifers of the types that had come in dur- 

 ing the Permian, and kindred new ones, were prominent, 

 while the cycadean group was still in a stage of deployment 

 and occupied the central place of interest. . . . The Triassic 

 conifers bore the scrawny aspect of the walchias and voltzias 

 of the Permian. ... It does not appear from the record that 



Am. Jour. Sci.— Fourth Series, Vol. XXXIII, No. 197.— May, 1912. 



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