22 TERTIARY INSECTS OF NORTH AMERICA. 



6. Ferruginous shale; unfossiliferous- 1.5 



7. Resembling No. 5, but having no conchoidal fracture; stems of plants, insects, and a small 



bivalve niollusb 9 



8. Very fine gray ocbreous shale; non-fossiliferoiis 0. 5 



9. Drab shales, iuterlaminated with finely divided paper ishales of light-gray color; stems of 



plants, reeds, and insects 46 



10. Crumbling ochreous shale; leaves abundant, insects rare 7.5 



11. Drab shales; no fossils ^ 7.5 



12. Coarse, ferruginous sandstone; uo fossils 3.8 



13. Very hard drab shales, having a conchoidal fracture and filled vrith nodules; unfossilif- 



erous 63 



14. Finely laminated yellon-ish or drab shales; leaves and fragments of plants, with a few 



insects 30 



15. Alternating layers of darker and lighter gray aud brown ferruginous sandstone; no fossils.. 10 



16. Drab shales; leaves, seeds, and other parts of plants, with insects, all in abundance 61 



17. Ferruginous, porous, sandy shales; uo fossils 5.7 



18. Dark gray aud yellow shales ; leaves aud other parts of plants 9 



19. luterstratified shales, resembling 17 and 16; leaves aud other parts of plants, with insects.. 17. 8 

 20 Thickly bedded chocolate-colored shales; no fossils 41 



21. Porous yellow shale, interstratitied with seams of very thin drab-colored shales; plints -. 7.5 



22. Heavily bedded chocolate-colored shales; no fossils 30 



23 Thinly bedded drab shales; perfect leaves, with perfect aud imperfect fragments of plants, 



and a few broken insects 20 



24. Thinly bedded light-drab shale.<, weathering very light ; without fossils 20 



25. Thick bedded drab shales, breaking with a conchoidal fracture; also destitute of fossils.. 18 



26. Coarse arenaceous shale ; iiufossilifeious 9 



27. Gray sandstone, containing decomposing fragments of some white mineral, perhaps calcite ; 



uo fossils 178 



28 Coarse, ferruginous, friablje sandstone, with concretions of a softer material ; fragments of 



stems perhaps.. 60 



29. Thinly bedded drab shales, having a conchoidal fracture, somewhat lignitic, with frag- 



ments of roots, etc . . -; 25 



30. Dark-chocolate shales, containing yellowish concretions; filled with stems and roots of 



jilants .... ... 25 



Total thickuess of evenly bedded shales ("D," of Dr. Wads worth's note) above floor 

 deposits (Meters). . 6. 668 



Tlie bed which has been most worked for insects and leaves, and in 

 which thev are unquestionably tlie 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 aud 1) ; in other beds they 

 occurred only rarelv or in fragments. Plants were always abundant where 

 insects were found, but also occurred in many strata where insects were 

 either not discovered, such as Nos. 18 and 21 in the lower half and No. 6 in 

 the upper half, or were rare, as in Nos. 10 and 14 above the middle and No. 

 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 laminse, indicating 

 an enormous shower of ashes or a mud flow at the time of their deposition; 

 their character was similar to that of the floor-beds of the basin. 



