468 



SCIENCE. 



[N. S. Vol. VIII. No. 197. 



all to be Middle Cretaceous in age. This 

 conclusion seemed to be quite generally ac- 

 cepted and was apparently not questioned 

 until about two years ago, when an an- 

 nouncement was made, with some show of 

 authority, that the series is probably Juras- 

 sic in age. In regard to the correlation of 

 iihe several formations mentioned there can 

 be no question. The large amount of paleo- 

 botanical material available for comparison 

 has given opportunity for the identification 

 •of so many species common to them all 

 -that this conclusion is not only justifiable, 

 but inevitable, and the only question is 

 whether the correlation also demonstrates 

 that the several formations are Middle Cre- 

 iaceous in age. If any one of them is, 

 then they all are ; if any one is not, then 

 the others are not. 



In paleobotany, as in paleozoology, the 

 broad general facts are recognized that the 

 biological sequence is coincident with the 

 geologic sequence, and that the farther 

 back in geologic time the simpler and lower 

 in the scale of life were the organisms. 

 Hence, if we divide our fossil flora into the 

 three great classes of cryptophytes, gym- 

 nosperms and angiosperms, the sequence of 

 their appearance and periods of maximum 

 development would be in the same order. 

 The percentages of these classes in any 

 floras should, therefore, be a fair indication 

 of the relative ages of the floras. A typical 

 Jurassic flora, such as that of Siberia, con- 

 tains, roughly, the following percentages : 

 cryptophytes, 22 ; gymnosperms, 74 ; and 

 angiosperms, 4. The Older Potomac flora, 

 which is regarded as Lower Cretaceous, 

 contains the same classes in the percent- 

 ages of 39, 39 and 22 ; the Newer Potomac, 

 regarded as Middle Cretaceous, 8, 13 and 

 79 ; the Amboy clays, 6, 13 and 81 ; the 

 Dakota group, 1, 5 and 94. Similar ex- 

 amples of percentages are also calculated 

 for other floras regarded as Cretaceous in 

 age. The main fact, which is at once seen, 



is the manner in which the percentages of 

 the gymnosperms and angiosperms are re- 

 versed. Few angiosperms, and only those 

 of doubtful character, have been found in 

 any formation recognized as Jurassic, so 

 that when it was ascertained that in the 

 Amboy Clay flora and its equivalents the 

 angiosperms represent from 70 to 90 per 

 cent, of the entire flora there was little 

 hesitation in considering it as well ad- 

 vanced in the Cretaceous period. There 

 would be nothing inconsistent in regarding 

 the lowest of the Older Potomac strata as 

 Jurassic, but even there it would require 

 definite paleontologic evidence, while in re- 

 gard to the Amboy Clay series it is safe to 

 say that a Jurassic fauna will never be 

 found in connection with its flora. 



In face of the direct evidence of the fossil 

 flora, therefore, it would seem a very haz- 

 ardous undertaking, without ample evi- 

 dence in rebuttal, to draw the line of sepa- 

 ration between the Jurassic and Cretaceous 

 so that in the West the base of the Creta- 

 ceous would be represented by the Dakota 

 group and in the East by the clay marls of 

 of the Matawan formation. (The paper 

 was illustrated by tables of percentages and 

 charts.) 



6. Some Feldspars in Serpentine, in South- 

 eastern Pennsylvania. By Professoe T. C. 

 Hopkins, State College, Pa. Feldspar oc- 

 curs in this district as dikes or veinlike 

 masses in serpentine, sometimes attaining 

 a thickness of 20 to 25 feet. The most ex- 

 tensive area is in Chester county, extending 

 also into Lancaster county ; but there is 

 another area in central Chester county, 

 near the corundum mines. The feldspar is 

 snow-white to pink in color, and seems to 

 be wholly orthoclase. Some of the dikes 

 have been exploited to a depth of 60 feet. 



7. The Region of the Gausses, in Southern 

 France. By Rev. Horace C. Hovey, New- 

 buryport, Mass. Lofty tablelands in the 

 Departments of Lot and Lozere, along the 



