688 R. W. RICHARDS AND G. R. MANSFIELD 
the phosphatic beds above the Quadrant formation of certain 
areas (11) (1) in southwestern Montana. 
The Rex chert member is the conspicuous portion of the Phos- 
phoria formation, and because of its superior hardness it stands 
out in salient topographic features. ‘The phosphate shales on the 
other hand are comparatively non-resistant and the development 
of gulches along them is characteristic. 
Locally 50 to 75 feet above the base the Rex chert gives way to 
gray limestone and in other places a dark gray to black or purplish 
flinty or cherty shale occupies the major portion of the Rex chert 
interval, but more generally the shaly facies is present near the top 
of the section and is occasionally with difficulty distinguished from 
the basal portion of the Woodside shale. 
The Rex chert is generally non-fossiliferous but locally contains 
sponge spicules and casts of crinoid stems. Dr. Girty lists the 
following as the most characteristic species: 
Productus multistriatus 
Productus subhorridus 
Spirifer aff. cameratus 
Spiriferina pulchra 
Composita subtilita var. 
At a locality on Deer Creek in the Preuss Range Dr. Girty 
obtained the following fauna from the limestone facies of the 
Rex chert: 
Amphoporella laminaria 
Productus nevadensis 
Productus eucharis 
Productus multistriatus( ?) 
Camarophoria n. sp. 
The basal portion of the Phosphoria formation consists of 75 
to 180 feet of yellowish to brown phosphatic sandstones and shales 
with 1 to 3 economically important beds of rock phosphate, and 
occasional dark fetid limestones in beds and lenses ranging from 3 
inches to 2 feet in thickness. 
The fauna of the phosphate shales is an extensive one and has 
