64 ROYAL SOCIETY OF CANADA 



siuce glacial activity continued there so late." It is therefore impos- 

 sible at present to determine the age of these deposits from geological 

 evidence;, but a consideration of the relation of the locality to the pre- 

 sent distribution of Pseudatsuga may possibly offer some suggestion 

 toward that end. 



At the present time the genus Pseudotsuga is chiefly confined to 

 ihe Pacific slope of the Sierra and Coast Range Mountains, the centre 

 of distribution lying westward of the Sierras and ranging approximately 

 from latitude 51° to 39°, thus imcluding southern British Columbia, 

 western Oregon and Washington, and northern California.' But the 

 >pecies neverldieless spreads northward for a long distance, and. east- 

 ward over the entire Rooky Mountain region into Montana, the limit 

 being apparently defined by contact with the Prairie Region. In the 

 vicinity of Bozeman, the species projects from the general eastern limit 

 of distribution like a great spur, apparently following the foot-hills of 

 the Big Belt Mountains, which terminate there. Bozeman lies about 

 twelve miles to the westward of the southern terminal of the Big Belt 

 Range in longitude 111° 15' W., and latitude 45° 41' N.; a.id it is 

 therefore well within the Rocky Mountain region, and about 100 miles 

 to the west of the eastern limit which Prof. Sargent has assigned for 

 the distribution of Pseudotsuga.^ It would appear, however, from the 

 statement of Mr. Thorpe, that " the timber of the locality consists of 

 scrubby pine with a diameter of twelve inches, and that the fossil tree 

 is unlike anything now growing in that section of country," that there 

 must have been a local obliteration of the genus, possibly due to the 

 same causes which led to its withdrawal from the Prairie Region at some 

 time subsequent to the Eocene, since the occurrence of one species at 

 least informs us that during the Lignite Tertiary age it must have been 

 more or less abundant as far eastward as longitude 104° W. Whether 

 this recession from a formerly very wide distribution occurred at the 

 close of the Eocene, in the Miocene or subsequently to the glacial 

 period, we have no present means of ascertaining from our knowledge 

 of the geological distribution of the genus. So far, then, as our 

 knowledge of the genus itself goes, there is nothing which will in any 

 way afford a clue to the particular age of the deposits at Mystic lake, 

 and we may seek the aid of collateral evidence in the hope of ^^ocuring 

 fnrtber information. 



The genus Sequoia at present centres in a region which is largely 

 common to the centre of distribution for Pseudotsuga, though we have 

 abundant evidence that during Cretaceous time the two genera were 

 not only co-extensive on this continent, but tliat Sequoia itself was 

 known to Greenland and Europe. It is therefore evident that there 

 ' Tentli Census of the United States. Forestry Map. 



