276 GEOLOGICAL SURVEY OF THE TERRITORIES. 
Centimeters. 
- 15. Alternating layers of darker and lighter gray and brown ferruginous sand- 
stomes:(nofossile liao Beh Lat back a) ale en coli a et Reg 10 
16. Drab shales ; leaves, seeds, and. other parts of plants, and insects, all in 
album dame ise kee es ree GSES i NOS ees Ee A gr c/a A 61 
17. Ferruginous, porous, sandy shale; no fossils ..---....2--.---------.---- Bs 
18. Dark gray and yellow shales; leaves and other parts of plants ---.-.-.... ig) 
19. Interstratified shales, resembling 17 and 18; leaves and other parts of 
plants. wibbrinsectse: 20) 35 oe Se cl aa es Bek ela, Si eR a 17.8 
20. Thickly bedded chocolate-colored shales; no HOssilg oe uals Seas 41 
21. Porous yellow shale, interstratified with seams of very thin drab- idieaall 
Shnalests py lami se yaks SEER RY Se gS mE See EE be St i See 7.5 
22. Heavily bedded chocolate-colored shales; no fossils ......-.----.----.--- 30 
23. Thinly bedded drab shales; perfect leaves, with Saw and imperfect 
fragments of plants, and a few broken insects Te oe, ee 20 
24. Thinly bedded light-drab shales, weathering very light; without fossils; 
PDEDSS Uae Lan Oe 2 apse ET NR Perm i MR 20 
25. Thick bedded drab shales, breaking with a conchoidal fracture ; also des- 
PrbutelOt fOSstls ioe sees cies ke Me ae I Se ey aie Se Ut 18 
26. Coarse arenaceous shale; unfossiliferous.......-...----..-----+--------- io) 
27. Gray sandstone, containing decomposing fragments of some white mineral, 
perhaps calcite ; mo fossilee oe i Uh Maik Aes dbs vy Ua eel 178 
28. Coarse, ferruginous, friable sandstone, with concretions of a softer mate- 
tial; fra ements Of SHOMs oh eee eI Sica GL oe ae 60 (7) 
29. Thinly bedded drab shales, having a conchoidal fracture ; somewhat lig- 
nitic, with fragments of roots, SEG LLL GER, WA Id CES DES pe 25 
30. Dark-chocolate shales, containing yellowish concretions ; filled with stems 
and roots of plants 2 5aek Se ee ee pe mse am aaa 25 
Total thickness of evenly bedded shales (D of Dr. Wadsw orth’s note) 
above floor deposits... -- st a MANE SE Te AE ae SUS (meters) 6.668 
The bed which has been most worked for insects and leaves, and in 
which they are unquestionably the most abundant and best preserved, 
is the thick bed, No. 16, lying half way up the hill, and composed of 
rapidly alternating beds of variously-colored drab shales. Below this 
insects were plentiful only in No. 19, and above it in Nos. 7 and 9; in 
other beds they occurred only rarely orin fragments. Plants were always 
abundant where insects were found, but also oceurred in many strata 
where insects were either not discovered, such as beds 18 and 21 in the 
lower half and bed 6 in the upper half, or were rare, as in beds 10 and 
14 above the middle and bed 23 below; the coarser lignites occurred 
only near the base. 
The thickest unfossiliferous beds, Nos. 20 and 27, were almost uniform 
in character throughout, and did not readily split into laminae, indicat- 
ing an enormous shower of ashes or a mudflow at the time of their dep- 
osition; their character was similar to that of the floor-beds of the basin. 
These beds of shale vary in color from yellow to dark brown. Above _ 
them all lay, as already stated, from fifteen to twenty-five decimeters of 
coarser, more granulated sediments, all but the lower bed broken up and 
greatly contorted. These reached almost to the summit of the mesa, 
which was strewn with granitic gravel and a few pebbles of lava. 
Specimens of these upper irregular beds, and also of the underlying 
shales, were submitted to Dr. M. E. Wadsworth, of Cambridge, who 
caused thin seetions to be made from them, and has furnished the fol- 
lowing account of their microscopical structure: 
TUFA FROM FLORISSANT. 
The method and scheme of classification employed here is that briefly sketched in 
the Bulletin of the Museum of Comparative Zodlogy (vol. v, pp. 275-287). By this sys- 
tem only do we think that the inclosed fragments could be named, for they contain 
so few crystals that in most cases the base is the principal thing upon which the 
decision must rest. 
