1902.] Loomis, American Jurassic Stratigraphy. 4*-*3 



two or three Baptanodon vertebrae were discovered, and 

 probably came from this horizon in some of the nearby ex- 

 posures. In the centre of Wyoming this layer has a purple 

 hue, but is otherwise similar. 



A sandy limestone or shell sandstone (No. 5) usually fol- 

 lows, which carries several invertebrate marine forms. At 

 the Belle Fourche station, this layer held Amaltheus cardi- 

 formis, u'Egoceras tumidus v. Buch, Ostrea strigulecula W., 

 Tancredia inornata M. & H., Pscudomonotis curtaW., P. orhic- 

 tdata W., Dosinia jurassica W., Trigonia sp., and Pholadomya 

 sp. This fauna with some variations is widely distributed at 

 this horizon.' 



From this horizon to the top of the marine Jurassic there 

 is no uniformity in the character of the beds, usually, as in 

 the Belle Fourche section, the clays alternating rapidly with 

 thin beds of sandstone. The Salt Creek section has soft sand- 

 stones alternating with denser ones. The Beaver Creek sec- 

 tion has nothing to represent the alternations. In central 

 Wyoming there are several clays and sandstones. There is 

 no uniformity except in the rapidly changing character of the 

 deposits. 



The top of the marine beds is a green clay (No. 12) of vary- 

 ing texture. The change to fresh- or brackish-water is a 

 gradual one, so that a distinct boundary is difficult to find, but 

 this bed is the highest in which any trace of marine life was 

 found, and is, therefore, used here as a convenient separating 

 horizon. 



The base of the freshwater deposits is a bed of sandstone 

 (No. 13), varying greatly in thickness and in character. 



No. 14 is a layer of green clay, the lowest in which any traces 

 of Dinosaurs were found. On the north side of Inyan Kara 

 Peak a few fragments of sauropod limb bones occurred; and 

 near the Sheldon P.O. section a few foot bones were found at 

 this level. At the Belle Fourche station traces of Dinosaurs 

 also occurred. In all cases the bones were uniformly hard, but 

 very scarce. 



' At the Sheldon P. O. station there occurred Camponecles platissijormis W., Tan- 

 credia warreni M. & H., T. bulbosa M. & H., Avicula tnucronata W., and Ostrea strigu- 

 lecula M. & H. The Kara Peak section had Amaltheus cardiformis M. & H., jEgoceras 

 tumidus V. Buch, and P seudomonotis curta W 



