218 OLDER MESOZOIC FLORAS OF UNITED STATES. 
American beds conform in all respects with the older classification, 
still proves a convenient and more or less satisfactory basis of sub- 
division. These general heads may be made to designate the three 
parts, I, IJ, and III, of the paper, and each of the parts may then be 
conveniently further subdivided into lesser heads dealing with the 
smaller geological groups or formations, designated for the most part 
by special names derived from localities where each is best exposed. 
In view of the considerable magnitude which such a memoir is found 
to assume, and especially of the impossibility of having all the illustra- 
tions prepared in time to be embodied in the Twentieth Annual 
Report of the Survey, it has been necessary to make a more general 
subdivision of it into two papers, one on the Older Mesozoic (Parts I 
and II), and the other on the Younger Mesozoic, or Cretaceous, and 
to confine the present paper to the former of these subdivisions, the 
matter for which is ready, leaving the other subdivision to form the 
subject of a second paper to be published in a subsequent report. 
PART I. 
THE TRIASSIC FLORA. 
There are certain beds which are generally admitted to belong to 
the great series called Triassic in all parts of the world, and the fossil 
plants only help to confirm the conclusions on this point which have 
been drawn from stratigraphical considerations and from other forms 
of life. It so happens, however, that the paleobotanical record is 
here very incomplete, and there is no adequate evidence that any 
plant remains have thus far been found in any but the uppermost 
portion of the Triassic series. It is true that Mr. Benjamin Smith 
Lyman, of the Pennsylvania Geological Survey, argues for a great 
thickness of the Triassic beds in Bucks and Montgomery counties, 
Pennsylvania,’ claiming that they extend into the Permian and 
contain the remains of Calamites and Lepidodendron, but no one 
else finds the same conditions, and Mr. Henry B. Kimmel, after an 
exhaustive study of these beds in the adjacent State of New Jersey, 
with Mr. Smith’s results before -him, finds reasons for doubting his 
conclusions, and reduces the thickness from 27,000 to 12,000 or 15,000 
feet by the discovery of faults.’ 
With regard to the fossil plants, Mr. Lyman admits that the sup- 
posed Calamites was never submitted to a competent specialist, and it 
is altogether probable that it represents the stem of a large Equisetum, 
as, for example, 4. Fogersi? (Bunb.) Schimp. It must be remem- 
1Proc. Am. Philos. Soc., Vol. XX XIII, pp. 5-10; 192-215; Pennsylvania State Geological Survey Sum- 
mary, Final Report, Vol ITI, Pt. II, pp. 2689-2638. 
2 Annual Report of the State Geologist of New Jersey for 1897, p. 138. 
