FLINT BED ABOVE THE MANHATTAN STONE. 47 



10. MijnJind kmimsenais, Shum. {rr) 



11. MyaVnm pcratttniuata, M. and H. (/•/•) 



12. Pinna peracnta, Shum. (rr) 



11). BeUcrophon cf. monifortkinus, N. and P. (/•/•) 



14. AUorisma cf. siibcnneata , M. and H. (rr) 



15. Schizodas cf. curtiforme, Walcott. (rr) 

 10. MacrochiUna anguUfera, White (?). (r) 



FIRST FLINT BED ABOVE THE MANHATTAN STONE. 



It^ Cliaracter and Po--<itioii. — The next prominent stratum above the 

 Manhattan stone is a limestone containing an abundance of chert, which 

 is crossed by the road near the brow of the hill on the east side of Seven- 

 mile creek about 11 miles north of the exposure of IManhattan stone. 

 The barometer made this ledge 122 feet higher than the top of the Man- 

 hattan limestone, and it is the lowest of the so-called " flint ledges." 



Bed IS of Meek and Hay den. — This stratum is bed 18 of Meek and 

 Hayden's section, Avliich was described as — 



"A Hght gray and whitish magnesian hmestone, vontnmmg Sp I rigera, Orthisina 

 umhracidiim (?), 0. shnmcwdinna, Produdns calhounUnius, Acanthocladia amerkuna 

 and undetermined species Cyathocnnus. Lower part containing many concretions 

 of tiint. Fort Riley and on Cottonwood creek." * 



The sum of the several beds between the base of this "flint ledge" 

 and the top of the Manhattan stone is 109 feet, as reported by INIeek and 

 Hay den. 



^' Fifth cherty Limestone''^ of Swallow. — The same stratum forms bed 

 number 62 of Swallow's section, which is called the " fifth cherty lime- 

 stone," and described as " a light drab and buff cherty magnesian lime- 

 stone, 12 feet," containing Productus calhmtnianus, Chonetes mucronata, 

 Orthisina like nmhraculam, Athyrls like snhtllita, and Crinoids, exposed 

 near Fort Riley.f 



According to Swallow's section, the l)eds between the IManhatten stone 

 and the " fifth cherty limestone " vary in thickness from 124 to 153 feet. 

 'J'his " flint bed " forms the top of the steep bluff one-half mile west of 

 Ogden,at the eastern line of the Fort Riley Military Reservation, where 

 according to the barometer, it is 105 feet above the highway, which is 

 near railroad level. The ledge is jdainly exposed along the bluff to the 

 west, and after crossing Three-mile creek it shows near the summit of 

 the sharp point west of the creek and about 50 feet above the liijrhway. 



" Wrefo'-d LinicHlone " of Ha,}/. — Tliis cherty ledge occurs in the lower part 

 of the Fort Riley section, which recently has been well described Ijy 



*Proc. Acjid. Nat. Sci., Phila., vol. xi, p. 17. 

 t Prelim. Rept. Geol. Surv. Kunsus, p. 14. 



