NATURAL SCIENCES OF PHILADELPHIA. 39 



the further developments of palseontological science in confirma- 

 tion of this position. 



As previously remarked, there has been found in the Carboniferous 

 strata of Morris, Illinois, a larva that has been referred to the 

 Arctians or woolly-bears. Granting the truth of this identification 

 for the sake of argument, the period of time that has elapsed since 

 the Carboniferous arctian flourished, down to the ushering into 

 existence of the Jurassic sphinx, has been ample, no doubt, for the 

 gradual evolution of an Arctian into a Sphinx through inter- 

 mediate forms. The fact that Tineids are not found in Carbon- 

 iferous strata is no argument for their non-existence. If the 

 Tineids of those early days had many points in common with ex- 

 isting types, it is only under the most favorable conditions that 

 parts of them could be preserved. 



That these conditions did not exist during the Triassic period, 

 is inferred from our knowledge of the disturbances which took 

 place in America, and the shallow basins both of fresh and salt 

 water that existed in foreign localities where this formation is de- 

 veloped. Evidences of disturbance occur in this country in the 

 tilted and displaced condition of the beds constituting the forma- 

 tion. This tilting is, doubtless, due to mechanical force, very 

 gradual in its action. Still further evidence exists in the profound 

 subsidence which has been shown to have been in progress in 

 regions of depression, occupied by the strata. Such a subsidence 

 would obviously have brought a strain upon superincumbent beds, 

 and sooner or later would have produced fractures and disarrange- 

 ment. The injection of igneous rocks which have intersected sand- 

 stone strata, affords still another proof. In our Triassic regions, 

 rocks of igneous origin are intimately connected with rocks of 

 aqueous origin. Throughout most of the European sandstones 

 and marls of this period, the occurrence of ripple-marks, rain-drop 

 impressions, and cracks from drying, plainly show that the strata 

 are of shallow-water and mud-flat origin; and the salt which has 

 been found and referred thereto, points to the existence of flats that 

 were exposed to occasional inundations of the sea, where the salt 

 water underwent evaporation. 



It is evident that in America where the greater disturbance of 

 the strata has occurred, as indicated above, such light and airy 

 creatures as moths would stand but a slim chance of leaving the 

 slightest vestiges of their remains imbedded. The tilting and 



