372 



OX THE EVIDENCE AFFORDED BY THE FOSSIL PLANTS OF 

 POINT OF ROOKS IN EEGARD TO THE GEOLOGICAL AGE 

 OF THE FORMATION. 



Before piirsaing the descriptiou of the species recognized from speci- 

 mens obtained from localities others than Point of Eocks since the pub- 

 lication of the last annual report of Dr. F. V. Haydeu (1873), it is 

 advisable to consider the characters of the group of plants described 

 above in relation to its geological affinity. 



The first of the species described, Lemna f hullata* is, to my belief, 

 identical with what has been published by Professor Dawson under the 

 name of Lemna sciitata, as remarked in the description of the species ; 

 for probably the first description was made from a small number of more 

 imperfecfc specimens than those which I have at my disposal. Though 

 we have one single kind of vegetable organism as proving the relatipu 

 of the strata where the remains have been found, they are of such 

 a peculiar character and unique form that we ma}^ admit their rela- 

 tiou as proved.f Now, the species enumerated aud described in 

 the Canada report are representatives of two groups, separated as 

 the Porcupine Creek group, including Souris River, and the Great Val- 

 ley or Pyramid Creek group, both positively recognized as of Tertiary 

 age by stratigraphy and lithology in the remarkably clear and instruct- 

 ive report of Prof. George Mercer Dawson. He describes (p. 86) the 

 first exposures of the Tertiary, overlying the Cretaceous of the Pembina 

 Valley, as consisting of hard beds of sandstone, which form the base of 

 the Lignite Tertiary. One of his sections (illustrated in PL III, fig. 2, of 

 the report, and described in p. 89), shows very perfectly the distribution 

 of the strata in some localities of those Lignitic formations of Canada, 

 aud is especially remarkable for the great number of its beds of lignite, 

 seven in number, averaging altogether seventeen feet six inches of coal 

 in a section of fifty-seven feet seven inches of measures. The section is 

 as follows : 



Ft. lu. 



1. Prairie sod — mixed shale and drift 7 



2. Lignite 6 6 



3. Grayish sandy shale (about) 4 



4. Lignite 1 C 



5. Grayish and yellowish well-stratified clays ^ 14 



6. Nodular iron-stone 4 



7. Grayish and whitish clay 2 



8. Carbonaceous shale 1 . 



9. Gray soft sandstone . . . . , 1 8 



10. Lignite 1 



11. Gray and yellowish laminated sandy clay , 5 



12. Iron-stone (nodular) 3 



13. Lignite 1 7 



14. Carbonaceous shale 1 6 



15. Lignite 2 2 



1(>. Gray sandy clay 2 



17. Lignite 1 5 



18. Sandy under clay, with large aud small roots, badly preserved . 1 6 



19. Lignite 3 2 



20. Grayish sandy clay , 



57 7 



•■ The specific uame is cbanj;ed in coDsideiation of the v.iscnlar form of most of the siieciiuens. The 

 generic relation has to be modified also when it is more clearlj' recognized. 



t Another species, enumerated by Professor Dawson, Oornus acuminata, Newby., as present in the 

 Tertiary of Canada, is also I'onnd at Black Butte. 



