NOTE ON FREMONT'S COLLECTION. 207 



Cycadeoideas, is a point that at once suggests either a change in climate in 

 the interval between the fossilization of the two groups or, if they con- 

 tinued to exist near each other in time, the presence about the Jurassic 

 fresh-water lake of areas with diverse climatic conditions. In the Black 

 Hills country, at least so far as I have noticed, there is likewise a corre- 

 sponding difference in the size of the accompanying silicified tree trunks. 

 Many of the Araucarioxylons of the upper cycad bed were of immense 

 height and size, rivaling the Norfolk Island pines of the present, while, on 

 the contrarj^, I have never found markedly large trunks in connection 

 with the Cycadella horizon, although they may occur farther west in 

 Wyoming. That any great change took place is not argued. The Cyca- 

 dellas may have grown in dry or arid situations, or in a climate like that of 

 Florida, where the dwarf Zamias thrive while the Cycadeoideas bespeak 

 moister and more distinctly tropical conditions. I first pointed out, in 

 a review in the American Journal of Science for May, 1900, page 386, 

 the fact that Cj'^cadella might have grown under less favorable conditions. 

 Seward likewise considers that t«hey may afford suggestions of value con- 

 cerning climatic conditions." 



The microscopic study of the Cj^cadella series which I have under- 

 taken in conjunction with the study of the Cycadeoidea has not been 

 completed, so that later it will perhaps be possible to discuss such ques- 

 tions as this with more safety. 



In connection with the relative position of Cycadeoidea and Cyca- 

 della, I should here mention that, under the direction of Professor Osborn, 

 Dr. F. B. Loomis has prepared especially satisfactory sections of the 

 better exposed Jurassic beds as seen farther west in Wyoming.'' While 

 this paper gives more exact information concerning the successive hori- 

 zons and their vertebrate fossils, no mention is made of plant remains. I 

 conclude that the bed Doctor Loomis numbers 22 is the cycad horizon 

 of the Freezeout Hills. 



NOTE ON FREMONT'S COLLECTION. 



In concluding this account of the known Jurassic floras of the United 

 States, it is well to call attention to the collection made by Fremont on 



a See Nature, October 24, 1901, p. 633. 



!'0n Jurassic stratigraphy in southeastern Wyoming: Bull. Am. Mus. Nat. Hist., Vol. XIV, Article XII, 

 pp. 189-197. 



