PART I CHAZYAN AND RELATED BRACHIOPODS—-COOPER 119 
a rare species. The Oklahoma specimens, however, do not seem to be related 
to the New York species. Anomalorthis sp. occurs in the Joins also, This genus 
thus indicates relationship to the Oil Creek formation which occurs just above 
the Joins. 
The occurrence of these two brachiopods in the Joins formation as well as in 
the overlying Oil Creek formation is interesting in connection with other fossils 
found in the Joins. The graptolite Didymograptus artus has been taken from a 
shaly zone and indicates relationship to the D. bifidus zone which occurs at the 
top of the Lower Ordovician (Canadian). On the basis of this graptolite, Decker 
assigns the Joins to the high Canadian. Such an assignment leads to difficulties, 
however, when the Joins is compared to the Pogonip sequence in Nevada. 
The brachiopod Desmorthis characterizes certain beds in the Pogonip which 
immediately overlie the Palliseria [Mitrospira| and Receptaculites zones several 
hundred feet in thickness. These zones are not represented in the Arbuckle 
sequence, consequently a disconformity of considerable magnitude occurs in 
that area. These zones in Nevada contain fossils of post-Canadian aspects which 
suggest that the Joins, despite Didymograptus artus, should be assigned to the 
early Middle Ordovician. 
Oil Creek formation.—This formation consists of sandstones, limestones, 
and shales. The sandstones are more than 200 feet thick in the eastern part of 
the mountains but thin to the west; the limestones thicken in the opposite 
direction from 20 feet to more than 500 feet. Several species of brachiopods oc- 
cur in the Oil Creek which have been incorrectly assigned to species from the 
Chazy group. Two of them were referred to Clitambonites: C. multicosta and 
C. porcia. The former is Anomalorthis oklahomensis Ulrich and Cooper, but 
the latter is not yet redescribed. The other Chazy species identified are Orthis 
acutiplicata and O. ignicula. The former is described herein as Orthambonites 
dinorthoides, new species, and the other as O. subconvexus, new species. This 
formation is correlated satisfactorily with the upper Pogonip, the part which 
contains Pseudomera nevadensis, because this trilobite also occurs in the Oil 
Creek formation. Lingulella sp. 2 is another Oil Creek brachiopod. 
McLish formation.—This formation consists of limestone, sandstone, and 
shale which reach a thickness of nearly 500 feet. Decker’s list of brachiopods 
includes a number of obvious misidentifications : 
Camarotoechia sp. = Ancistrorhyncha ? perplexa Cooper 
Dorytreta bella Cooper 
Glyptorthis sp. 4 
Orthambonites minutus Cooper 
*Orthis acutiplicata (Identification doubtful) 
O. ignicula 
*Plectambonites pisum 
Ptychopleurella oklahomensis Cooper 
*Rafinesquina champlainensis 
Sphenotreta sulcata Cooper 
*Strophomena incurvata 
Valcourea strophomenoides ? 
Zygospira recurvirostris = Dorytreta bella Cooper 
