HELL CREEK BEDS, CERATOPS BEDS AND EQUIVALENTS 221 



*Taxodium occidcnialc Newb. 

 *Tlinya intcrrupta N wb. 

 ^Trapa micro phylla Lesq. 

 ^Vibuniiirn anliqmtm (Newb). Hoi. 

 ^Viburnum ncwbcrryianum Ward. 

 ^Vibrunnm pcrplcxum Ward. 

 *Vibiirnum whympcri Hccr. 

 *Vilis xantholithensis Ward. 



[In the above list the species marked with an asterisk (*) are found also 

 in the upper member of the Fort Union.] 



To any one familiar with the flora of the Fort Union, it needs but 

 a glance at the species here listed to show how overwhelming is the 

 preponderance of the elements of this flora. As Doctor Newberry 

 long ago stated, it has a botanical facies which is unique and unmis- 

 takable. Attention is especially directed to the great development 

 of the genus Populus with 13 species, and the presence of such dis- 

 tinctive genera as Celastrus, Pterospermites, Elaeodendron, Grewi- 

 opsis, Cocculus, Marchantia, etc., while of the species it may be 

 stated that nearly half (37) have never been found outside this form- 

 ation, at least in this country. The following table presents graph- 

 ically the relations that exist between the flora of the lower member 

 of the Fort Union and that of other formations :^^ 



Total known Fort Union flora (including lower and upper members) 



about 500 



Total forms known from lower member 193 



Forms specifically identified in flora of lower member 84 



Of these 84 species there are common to upper member 61 



Common to lower member and Laramie 11 



Common to lower member and Montana • • • . 11 



** To the possible criticism that too much dependence has been placed in a 

 statistical comparison, rather than one based on relative abundance, the 

 following facts may be pointed out. The presence of a species in the list 

 does not, of course, indicate its abundance as an element of this flora, but 

 on turning back to the lists cf species recorded under each locality, it will be 

 noted that the frequent repetition of names shows the extent to which many 

 of the commonest and best known species are distributed. Thus Populus 

 amblyrhyncha occurs at 15 localities; P. cuneata at 1 1 localities; Sapindus 

 grandi' oliolus and Tazodium occidentale at 12 localities each, etc; indeed, 

 very few are present at a single locality only. In most cases the plants are 

 neither so well preserved nor so abundant in the lower member as they are 

 in the upper, and large collections are secured with more difficulty. 



