740 



SCIENCE. 



[N. S. Vol. XXIII. No. 593. 



not heretofore known. Among tlje well-de- 

 fined species from these areas are a large 

 number of ginkgos represented by leaves, male 

 inflorescences and also by the fruit. The 

 leaves, which furnish the most reliable data, 

 show Ginkgo sihirica to be not only well char- 

 acterized but abundant, while G. lepida is also 

 present. A much less abundant, but none the 

 less distinguishable type, is G. hwttoni 

 (Sternb.) Heer. We can not, therefore, longer 

 regard G. sihirica as the sole survivor of this 

 genus in the Lower Cretaceous. It must never- 

 theless be conceded that the occurrence of these 

 three species in the Kootanie of British Co- 

 lumbia and Alberta not only emphasizes the 

 basal character of that formation, but it di- 

 rects attention to the probability that its 

 lowest portion may even represent a transition 

 series — a conclusion which would bring it into 

 agreement with the views recently expressed 

 with respect to its equivalent in the United 

 States, the Lower Potomac. 



Our knowledge of the Shasta-Chico series 

 of California, originally defined in detail by 

 Diller and Stanton,' receives a fresh interest 

 by virtue of the treatment of the Shasta group 

 at the hands of both Professor Ward and Pro- 

 fessor Fontaine. The more recent recogni- 

 tion of this series in Oregon is of interest in 

 connection with the lately made observations 

 that it is also to be met with in British Co- 

 lumbia, where a newly described element of 

 the flora of this series as developed in Cali- 

 fornia {Gleichenia- gilhert-thompsoni Font.) 

 has been recognized. 



In discussing the Kootanie formation, the 

 valuable work of Sir William Dawson and Dr. 

 George Dawson is fully recognized, and corre- 

 lations with the United States horizons are 

 established. The value of this discussion is 

 greatly enhanced by the introduction of a list 

 of all the Kootanie plants recorded up to 

 1895. More recent studies of this formation 

 have extended this list in important partic- 

 ulars, while they have also brought out the 

 fact that the Kootanie flora of British Colum- 

 'bia and Alberta is more widely distributed on 

 the eastern slope of the Rocky Mountains than 

 has been hitherto recognized. 



'Bull. Qeol. Soo. Amer., 1894, pp. 435^60. 



Somewhat less than half the entire volume 

 (25Y out of 599 pages) is devoted to a dis- 

 cussion of the Older Potomac Flora, a term 

 which is here employed in the same sense aa 

 in his previous paper on the Potomac Forma- 

 tion (Fifteenth Ann. Eept. of the U. S. Geo- 

 logical Survey), representing in the main the 

 Potomac as it occurs in Virginia, and includ- 

 ing all beds of the same age occurring in other 

 states, but excluding those higher beds in 

 which the flora is mainly dicotyledonous. A 

 very large proportion of this part of the sub- 

 ject is devoted to an interesting and valuable 

 historical survey of our knowledge of the 

 Older Potomac Formation. 



In deriving conclusions from his examina- 

 tion of the flora. Professor Fontaine endeavors 

 to establish a correlation between the Potomac 

 formations of Maryland and Virginia, and in 

 doing so he points out that the term Lower 

 Potomac, as consistently used by him, embraces 

 the four members recognized by Ward as (1) 

 James Eiver, (2) Eappahannock, (3) Mount 

 Vernon and (4) Aquia Creek — the second be- 

 ing identical with what he had designated as 

 Fredericksburg, and the last or fourth being 

 the same as his Brooke beds. On the other 

 hand, the Maryland Geological Survey has 

 divided the entire formation into (1) 

 Patuxent, (2) Arundel, (3) Patapsco and (4) 

 Earitan in ascending order, but in neither of 

 these is there a question of division into 

 Lower and Upper Potomac. Under these cir- 

 cumstances. Professor Fontaine finds it neces- 

 sary to explain what is meant by Lower 

 Potomac. The Potomac of Maryland diflters 

 from that of Virginia in the absence of the 

 Mt. Vernon member, but the chief difference 

 which appears to distinguish the formation of 

 the two states seems to lie in the absence of 

 the Earitan from Virginia, while it is in force 

 in Maryland, and if the Earitan is to be re- 

 garded as Potomac, about which Professor 

 Fontaine appears to have some doubt, then it 

 constitutes the Upper Potomac, while all be- 

 low is Lower Potomac. This conclusion is 

 apparently based upon the observation that 

 there is essentially only one great break in 

 the continuity of the flora, and that occurs in 

 passing from the underlying beds to the Am- 



