April 13. 1893] 



NATURE 



557 



In Western Canada, in the Rocky Mountains, and in the 

 Queen Charlotte Islands (latitude 55") we have a lower creta- 

 ceous flora, characteristically mesozoic, and even allied to the 

 Jurassic. Two of its characteristic species are closely allied to 

 Divon eduli of y\^%\co{Divonites Colnmhianu! 2lx\A D. borealis, 

 Dawson). Along with these are species of Zamites and of 

 Podozamites, and leaves of Salisburya, very near to those 

 described by Heer from the so-called Jurassic of Siberia. The 

 lowest beds of this series contain no angiosperms ; but in beds 

 a little higher these begin to occur. This has been named in 

 Canada the Kootanie flora, from the river of that name in the 

 Rockies. The late Dr. Newberry, in one of his latest papers, 

 described the same flora with identical species as occurring in 

 Montana, and it coincides in part with the Potomac flora of 

 Fontaine in the south-eastern states. Its character and dis- 

 tribution show an extension of warm climate from Florida to the 

 Queen Charlotte Islands, coincident with a great northward 

 extension of the warm waters of the Gulf of Mexico, which in 

 my judgment is sufficient to account for the climatal con- 

 ditions. This lower cretaceous flora may be considered to 

 be Neocomian in age, and to correspond with the Wealden of 

 England, and the Komeof Heer in Greenland, which shows the 

 extension of at least a temperate climate beyond the latitude of 

 60=. 



The middle cretaceous brought in a still greater extension of 

 the warm Mediterranean Sea of interior North America, indi- 

 cated by the chalky foraminiferal Niobrara beds of the United 

 States geologists, which extend into Canada. North of these 

 marine beds, however, we have in Canada, in N. lat. 55°, the 

 Dunvegan sandstones and shales, which hold not only cyca- 

 daceous plants but a rich angiospermous flora, including such 

 warm temperate genera as Maguolia and Laurus, with more 

 northern forms as Betula and Populus. This we regard as a 

 middle cretaceous flora, in its older part approaching the well- 

 known Dakota flora of the United Slates, and corresponding to 

 the Atanc of Heer in Greenland. The cliaiate in this period 

 must have been humid, equable, and temperate, all around the 

 great American Mediterranean ; but it is not impossible that our 

 Dunvegan collections may include some plants of mountain 

 districts mixed with those of lower grounds. 



This was succeeded by the upper cretaceous, in the older part 

 of which we have the magnificent flora of the coal series of 

 Vancouver Island, which represents a Pacific coast flora, with 

 fan palms, live oaks, and other trees comparable with those of 

 modern Georgia and Florida. By this time, however, there 

 would seem to have been a geographical separation between the 

 Pacific coast and the plains, as the latter have not yet afforded 

 anything equiv.ilent to the Vancouver flora, and there are some 

 indications that, toward the close of the cretaceous, the climate 

 was cooler than previously. This is equivalent to the Patoot 

 series of Heer in Greenland. 



The Laramie period proper, that of the lignite tertiary for- 

 mations of the plains, seems to indicate a swampy and lacus- 

 trine condition of the interior plateau, and the rich angiosperm- 

 ous and gymnospermnus flora of this time, characterised very 

 markedly by species of Plalaniis and Sti/uoia, has a temperate 

 aspect in Canada, as far north as the McKenzie river. It cor- 

 responds with the so-called miocene of Heer in Greenland, but 

 is shown by stratigraphy and by its affinity with the eocene of 

 England and Scotland, as described by Mr. Starkie Gardner, to 

 be of that age if not constituting a transition group between the 

 cretaceous and tertiary. The paliEobotanists of the United 

 States, at first, following Heer, regarded this flora as miocene. 

 More recently some are disposed to consider it upper cretaceous. 

 In Canada it has all along been regarded as paleocene or 

 eocene, and so far as its flora is concerned this i-; its true 

 position. In a recent number of Nature I see that Prof. 

 Oshorn is disposed to regard the small mammalia of the Laramie 

 of the United States as of eocene affinities. If so, they will 

 agree with the plants. It seems more difficult to account 

 for the great northward extension of the Laramie temperate 

 climate than for that of the preceding cretaceous, as the great 

 Mediterranean of the latter seems to have dried up, though still 

 existing in part, or replaced by swamps and lakes. Possibly 

 some other arrangement of the warm Atlantic currents, as sug- 

 gested by Mr. Starkie Gardner, may have produced some eflFect, 

 in conjunction with obstruction of the Arctic currents, and a 

 lower level of Greenland. 



The general bearing of these facts on American climate is that 

 we have no evidence of a tropical climate in Northern Canada 



NO. 1224, VOL. 47] 



or Greenland, but that both the geographical and botanical facts 

 indicate a warm temperate climate, at least in the cretaceous 

 period, and that in the earlier eocene the climate was becoming 

 cooler and less equable. 



We have little to show for the miocene ; but what there is, as 

 in the Similkameen flora of British Columbia, would go to show 

 a cooler climate and more of local variation. 



I have little faith in attempts to deduce a mean temperature 

 in degrees of Fahrenheit from fossil plants ; but if carefully 

 collected, so as to keep separate those that belong to diffierent 

 horizons, and if studied in strict relation to the geological con- 

 ditions of their occurrence, they must affijrd excellent general 

 indications of climate. Allowance must, however, be made just 

 as in the case of animal fossils, for diflerences of station, altitude, 

 &c., and for extent of probable driftage or occurrence in situ.^ 

 In studying large collections of our mesozoic and tertiary fossil 

 plants, from different localities and horizons, I have as a geologist 

 naturally had reference to these points, and the work of such 

 men as Selwyn, Richardson, G. M. Dawson, and Mr, Connell 

 has left nothing to be desired as to careful collecting and deter- 

 mination of stratigraphical relations, while the study of animal 

 fossils by Mr. Whiteaves has gone on /an /ajj« and in harmony 

 with that of the plants. 



I sympathise with Mr. De Ranee in his defence of Heer's 

 studies of the Greenland plants, for I know that my own work 

 in Canada would be liable to still more severe criticism. It 

 must be borne in mind that the palseobotanist has very im- 

 perfect material, and that he is always liable unconsciously to 

 multiply species. If, however, his names serve to designate 

 the things, and if their geological relations are known, an im- 

 portant work has been accomplished — always, however, pro- 

 visional and liable to correction as new discoveries are made. 

 One of my Kootanie leaves is scarcely distinguishable on the 

 one hand from Heer's Salisbtuya sibirua, and on the other 

 from Lindley's Cyclopteris digitata, even when I have specimens 

 of both to compare it with. All may be the same, though re- 

 ferred on the one hand to ferns, on the other to coniferae, and 

 this may not be settled till specimens in fruit are found. But 

 in any case something has been done, and a widely distributed 

 vegetable form has been recognised at a particular stage of the 

 world's history. 



I hope to discuss some of these points more fully in a work 

 now in the press. Wm. Dawson. 



Augusta, Georgia, March 13. 



P. S. — Since writing the above I have obtained access to a 

 copy of Dall and Harris's "Neozoic Correlation Papers," - 

 which throws some additional light on the cretaceous and eocene 

 floras of Alaska, which, from its high northern latitude, affords 

 a good term of comparison with Greenland. It would appear 

 that fossil plants occur at two horizons. One of these (Cape 

 Beaufort), according to Lesquereux and Ward, holds species of 

 Neocomian age, equivalent to the Kootanie of British Columbia 

 and to the Kome of Greenland. The other, which occurs at 

 several localities (Elukak, Port Graham, &c.), has a flora 

 evidently of Laramie (eocene) age, and equivalent to the " mio- 

 cene " of Heer and Lesquereux and to the McKenzie river and 

 lignite tertiary of Canada. The plants are accompanied by 

 lignite, and evidently in silu, and clearly prove harmony with 

 Greenland and Northern Canada in two of those periods of 

 high Arctic temperature indicated above. 



Notes on a Spider. 



I SEND you the following notes on a spider, whose curious 

 habits I had an opportunity of observing, last year, on the West 

 Coast of Africa : — 



In the month of August, 1892, I was travelling by hammock 

 from Chama to Sekundi, two small towns on the Gold Coast. 

 'I hat part of the country is somewhat hilly and is covered with 

 " bush " and other forest growth. The road skirts the sea-shore, 

 sometimes following the beach itself, at other times taking turns 

 inland and winding round bases of small hills. 



It was about three in the afternoon and I was being leisurely 

 carried along by my bearers, when I noticed in the bushes that 

 bordered the path something which appeared to me to be a sort 

 of white flower, 



1 Ward, of the U.S. Geo!. Survey, has directed attention to these points 

 in an excellent paper published by the Survey. 

 -• Bulletin U.S. Gcol. Sinvey, 1892. 



C C 2 . 



