l6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 75 



corresponds to the lower zone of the Sarbach formation of the Clearwater 

 River section, and which may represent the fauna near the base of 2b of this 

 section. The fauna includes (locality i6z) : 



Receptaculites 



■Obolus sp. undt. 



Obolus sp. undt. 



Protorthis tones Walcott 



Asaphiis ? 

 A mile to the northwest beneath the shale carrying the graptolites noted 

 under 2a, there is a series of light gray, more or less ferruginous, brown 

 weathering, thin-bedded silicious cherty layers with annelid borings running 

 through them in all directions ; the borings are filled in with a dark brown, 

 fine arenaceous material that disintegrates more readily than the matrix, leav- 

 ing many holes and cavities. P^^^ utters 

 Estimated thickness 250 76.2 



It is probable that these beds represent a local development below the base 

 of 2a. 



The Wonah Ridge portion of the Sinclair Canyon section supplements the 

 upper portion (p. 21) of Stoddart-Dry Creek section and gives a definite limit 

 to the upper horizon of the Mons formation, also the thickness of the Ordo- 

 vician Sinclair shales between the Mons and the Wonah quartzite. 



OZARKIAN 



MoNs Formation : P,,t Meters 



I. More or less irregular dove gray limestone in layers and 

 bands varying in thickness from a few inches (i to 10, 

 2.5 to 25.4 cm.) to 2 to 6 feet (.6 to 1.8 m.) and inter- 

 bedded at irregular intervals in a gray calcareous impure 



shale 545 166. i 



Strike near base of exposure above talus slope. Strike N. 



45° W., Dip N. 20° N. E. 

 Fauna. — At summit (2ih) : 



Obolus sp. 



Lingulepis cf. acuniinafa (Conrad) 

 Xenostegium 2 sp. 

 Fragments of trilobites 

 Just above the talus slope on Wonah Ridge, about 500 feet 

 (152.4 m.), below summit of i, fragments and sections 

 of Osarkispira leo Walcott occur in a hard dove colored 

 layer of limestone. 

 A thin layer of hard gray limestone a little below the 

 Ozarkispira leo layer afforded a few cranidiae and a 

 pygidium of Hystricurus sp. (Locality 2iq.) 



Note. — I did not find in Sinclair Canyon that portion of the Mons formation 

 that occurs between the Ozarkispira leo zone of the Wonah Ridge section and 

 the Hungaia faunule zone that occurs in the highest beds exposed of the Mons 

 formation, east of the great fault, as found at the first bridge near the mouth 



