ipoi.] Loomis, yurassic Stratigraphy in JVyomifig. 1 95 



In Bone Cabin Draw this green clay is overlaid by a second 

 layer (No. 27) of concretions, so that the ' Nine Mile Quarry ' is 

 between two such layers. 



No. 28 is a gray sandstone in which the rich Bone Cabin 

 Quarry is situated, and also the Stegosaurus Quarry. The sand- 

 stone varies extremely in hardness, being, in the south part of 

 Bone Cabin Quarry, soft and mixed with considerable clay so that 

 it is workable with an awl. In the northern part of the quarry, 

 however, there are bands of the firmest sort of sandstone. In 

 Como Bluff the layer is clay with merely an admixture of sand. 

 Bone Cabin Quarry has yielded a great variety of genera: Diplo- 

 docus, Morosaiirus, Brontosaunis^ Allosaurus, Ceratosaitrus, Camp- 

 tosaurus, Stegosaurus, as well as several genera of carnivorous 

 Dinosaurs; also Compsemys and Gouiopholis. 



On the surface of this sandstone is usually a 4-inch layer of 

 flint, No. 28a. 



No. 29 is another green clay showing the ' joint ' structure 

 similar to No. 26. Several of Marsh's quarries are in this layer. 



The series ends with a soft bluish green clay in which I have 

 never seen fossils. This completes the Jura. 



A cap of Dakota sandstone overlies the Jura, near the base of 

 which is a narrow (2-6 feet) band of soft black, or occasionally 

 red, sandstone. This band is colored by iron and of interest as 

 having lately yielded a collection of bones probably crocodilian. 



There is some difficulty in comparing the foregoing sections 

 with those of Logan and Knight, as these authors give fewer 

 beds. Marsh divided the Jura into three horizons, Hallopus, 

 Baptanodon, and Atlantosaurus beds. The Hallopus beds do 

 not occur in southeastern Wyoming. The Baptanodon beds, 

 according to Marsh, included all of the lower Jurassic, which 

 has since been subdivided, but the term Baptanodon is now ap- 

 plied to a single layer (No. 4) in which these reptiles occur. 

 When this term is restricted to a single layer, the lower strata are 

 without designation; so for these. Knight has proposed the term 

 Shirley stage, which shall include all the marine Jura; that is, 

 beds 2-12 inclusive. The exact boundary between marine and 

 non-marine is difficult to locate, but bed 13 has furnished some 

 Dinosaur remains and may therefore be associated with the beds 

 in which Dinosaurs are abundant. Then beds 13-30, inclusive, 



