TRIASSIC PERIOD. 415 



parallel with the mountains or the coast-line, and occupy synclinal 

 valleys formed in the course of the folding of the Appalachians. 

 They lie unconformably on the folded crystalline rocks, and thus 

 show that they are subsequent in age. On the map, page 133, the 

 narrow areas are obliquely lined from the right to the left. One is 

 situated in the Connecticut valley, and extends from New Haven 

 to northern Massachusetts; others are distributed over the region 

 between the lower Hudson (the Palisades) and the southern part 

 of North Carolina. 



The map of Pennsylvania on p. 323 shows the position of the 

 area in that State, it being distinguished by the same oblique lining 

 as on the general map. It takes the same westward bend with the 

 Appalachians of the State, retaining that parallelism with the 

 mountains which characterizes the areas elsewhere, and thus cor- 

 responding in direction with the synclinal valleys. 



The rock is in general a red sandstone, passing in some places 

 into a shale or conglomerate, and occasionally including beds of 

 impure limestone. The brown building-stone of Newark, N.J., 

 and Portland, Conn., often called Freestone, and much used in the 

 city of New York and elsewhere, comes from this formation. Near 

 Eichmond, Va., and Deep River, in North Carolina, there are valu- 

 able beds of bituminous coal. 



In many regions the layers of rock are covered with ripple- 

 marks and raindrop-impressions, or penetrated with what were ori- 

 ginally mud-cracks, — all of which marks are evidences of exposure 

 above the water during the progress of the beds. 



In the Connecticut valley, and to some extent also in New Jersey 

 and Pennsylvania, the surface of the beds is sometimes marked with 

 the footprints of various animals, as Insects, Reptiles, and Birds ; 

 and Professor Hitchcock, who has made the tracks of the Connec- 

 ticut valley his special study, has in the Amherst College Cabinet 

 (at Amherst, Mass.) about 8000 tracks, averaging sixty-eight tracks 

 for each species of animal. There are also numerous specimens in 

 other collections in New England and elsewhere. 



On the Gulf border there are no Triassic rocks, excepting such as 

 may possibly be buried beneath later formations. 



The formation beyond the Mississippi which is supposed to be 

 Triassic consists of sandstones and marls of usually a brick-red 

 color, and often contains gypsum. It outcrops at the base of the 

 ridges of the Rocky Mountains, and covers wide areas. It is 

 largely developed west of the summit in the Colorado valley, espe- 

 cially about the region of the Little Colorado. 



(a.) Atlantic border. — The areas on the Atlantic border are as follow : — 



