20 jMesozoic flohas of umtkd states. 



I shall divide the Shinanimp into two somewhat distinct parts and 

 call the lower the Lithodench'on member and the upper the Leroux 

 member. 



THE IJTIIODKXDROX MEMBER. 



This division is the ec}uivalent of the Shinanimp conglomerate of 

 Powell, anfl I was at first disposed to retain his name under the rule of 

 priority, and did so in my preliminaiy paper," notwithstanding the far 

 greater development and marked change of character which it assumes 

 in t he upper part of the Colorado Valley. Attention has been called to the 

 fact that the use made l\y Major Powell of the name Shinarump conglomerate 

 for a part of a larger group which he called the Shinarump is likely to lead 

 to confusion and is generally objectionable. I shall therefore drop that 

 temi, except as descriptive of the conglomerate beds that occur in the 

 Shinarump, and shall call the part of the formation in which these con- 

 glomerates occur the Lithodendron member. This term is specially 

 appropriate not only because of the stone trees that constitute the 

 most prominent featui'e of the beds, but also because the name was 

 given by Lieutenant Whipple in 1853 to the stream or wash in which 

 petrified tnmks were found in great abundance by his exploring party 

 when it passed through that region.'' This was there called Lithodendron 

 Creek, and it was from the bed of this creek that the two trunks brought 

 to the United States National Museum in 1879 by Lieutenant Hegewald 

 were obtained, these being the only ones that have thus far been studied 

 from the standpoint of their internal structure. The creek lies in the 

 region where the Lithodendron beds attain their maximum development 

 and only a short distance from the Petrified Forest which it has been 

 proposed to set apart as a national park. 



Although perhaps the most prominent feature of this formation is 

 the so-called conglomerate, which sometimes is in truth deserving of that 

 name, and contains somewhat large but always well-worn pebbles and 

 cobbles derived from imderlying formations, it rarely happens that this 

 aspect of the beds constitutes the major portion of them. In the first 

 place, the conglomerate tends to shade off into coarse gravels and 



n Geology of the Little Colorado Valley: Am. Joum. Sci., 4th ser., Vol. XII, No. 72, December, 1901, 

 pp 401-41.3. 



'' Report of Explorations and Siiriey.s to asccrhiin the most Praotiiidjlc and KiDnoniical Konio for a 

 Kailroad from the Mississippi Kivcr lo ihc Pacific Ocean, Vol. Ill, 185(3, Pt. 1, pp. 73-7'r, Pt. U, p. 2S; Pt. 

 IV, pp. 43, 150, 151, 1G7. 



