4-8 F. II. KnowUon — Jurassic Flora of Oregon. 



Siberia. At first thought it may seem a far call from Cali- 

 fornia and Orei^-on to Sil)oria, but when it is pointed out that 

 there arc a number of connecting points at which the Jurassic 

 has been found in western British Columbia, southern and 

 western Alaska, and thence out on the Alaskan peninsula, it is 

 seen that we have here indication of a probable land connec- 

 tion between the continents in Jurassic time. 



In 1876 Heer* published his first paper on this flora which 

 included material from Kajamiindung and Ust-Bali, Siberia, 

 and the upper Amur iiiver, and Bureja in the Amur. This 

 was supplementedf in 1878 and 1880 by the study of further 

 material from the original localities as well as from the Lena 

 delta, etc. The number of species finally aggregated about 

 100, many of which have since been identified in widely differ- 

 ent parts of the world, the greatest number (16 specie's) being 

 common to the beds of Yorkshire, England. The age of the 

 Siberian deposits was fixed by Heer as that of the middle 

 Brown Jura (Dogger), which is about the equivalent of the 

 lower Oolite of Yorkshire. 



Following is the list of species common to California and 

 Oregon and eastern Siberia : 



Cladophlehis argntula Podozamites lanceolatus minor 



Cladophlehis acutiloba Podozamites lanceolatus latifolius 



Cladophlehis spectabilis Ginkgo digitata 



Tliyrsopteris Murrayana Ginkgo Huttoni 



Thyrsopteris Maakiana Ginkgo lepida 



Nilsonia orientalis Ginkgo siberica 



NiUonia parvula Seeds of Ginkgo 



Pterophylluin rajmahalense Pinus JSfordenskioldi 



Podozamites pulchellus Prachyphyllum, mamillare. 

 Podoiamites lanceolatus 



As Professor Fontaine has pointed out, the strata of Oregon 

 and California rival those of eastern Siberia in the develop- 

 ment of Ginkgos, and as he says, it is a noteworthy fact that 

 nearly all of the more important forms described by Heer 

 from those beds have similar forms in the Oregon strata. Cer- 

 tain of the forms, notably that known as Ginkgo digitata^ have 

 a distribution into somewhat later beds, but in these later 

 horizons, such for example as the Kootenai formation, they are 

 smaller and not present in such numbers. In fact the Ginkgos 

 in the Lower Oolite time were immensely developed in the 

 Amur region of Siberia and in the northwestern portion of the 



* Beitrage z. Jura-Flora Ostsibiriens u. d. Amurlandes. Mem. Acad. Imp. 

 d. Soi. St. Petersb. (Fl. Foss. Arct., vol. iv, Abt, 2), vol. xxii, pp. 1-122, pis. 

 i-xxxi, 1876. 



fOp. cit., vol. xxiv, 1878 (Fl. Foss. Arct., vol. v, Abt.. 1), pp. 1-26. pis. 

 i-vii. Op. cit., vol. xxii, 1880 (Fl. Foss. Arct., vol. vi, Abt. 1), pp. 1-34, 

 pis. i-ix. 



