452 University of California Publications in Geology [Vol. 10 



Fish scales are very numerous in the Mowry shales and fins are 

 frequently found, especially in the sandstone members. Pish teeth are 

 occasionally found, but the bony parts are rarely if ever encountered. 



Fish scales, teeth, and fins are very abundant in nos. 1, 2, and 3, 

 scales being especially numerous in no. 1. Scales are frequently found 

 in the upper members, but they are not so abundant as in the lower. 

 They are rather rare in no. 7. 



Several thin sections of Mowry shale from various paints of Wyom- 

 ing were examined. The following is a description of a specimen from 

 the southwest limb of the Emigrant Gap anticline, about 10 miles 

 west-southwest of Casper. In the hand specimen this is a very dark 

 gray, hard platy shale which splits readily into plates one-eighth to 

 one-half inch in thickness. When broken across the bedding it has a 

 somewhat conehoidal fracture. It weathers to a silvery gray color. 

 Fish scales up to three-fourths inch in diameter are common, and fins 

 up to four inches in length are occasionally found. In thin section 

 the color is brown, due to organic matter. In extremely thin sections 

 the color is very pale brown to brownish gray. Under crossed nicols 

 the material of the shale is shown to be largely isotropic, with a few 

 very minute fragments of quartz and feldspar. The shale cannot be 

 resolved into its constituents even with the highest power. 



A hard dark gray to black siliceous, somewhat sandy shale from 

 the Mowry of the Sunshine anticline shows very angular fragments 

 of plagioclase and quartz up to 0.20 mm. in size. These fragments 

 are very irregularly distributed, being rather closely spaced in some 

 areas and almost entirely lacking in others. The feldspar, which is 

 chiefly albite and albite-oligoclase, is equal in amount to, or slightly 

 predominates over the quartz. A sandstone from the Mowry of the 

 same locality shows angular fragments of quartz, plagioclase, and 

 occasionally a fine grained quartzite fragment embedded in a brown 

 calcareous matrix. No remains of diatoms were seen in any of the 

 slides examined and in only one slide were radiolaria found. These 

 were in a chert from the Mowry of Oil Mountain anticline, about 

 25 miles west of Casper. In the hand specimen this chert is dark 

 blue gray to black on the fresh surface, weathering to a dull white 

 or light gray, and breaks with a conehoidal fracture. The rock is 

 dotted with small dull white spots ranging up to one millimeter in 

 diameter. There are usually about forty to forty-five of these spots 

 to the square centimeter of surface. These spots become larger and 

 more numerous toward the weathered surface of the rock, and finally 

 this surface is covered with a dull white to gray film. In thin section 



