TYPICAL SUNDANCE AND MORRISON SECTIONS 255 



Feet 

 Jointed clay, greenish, witli small coucretious. Brontosaurus, 

 Diplodocus, and Morosaurus. First appearance of PlanorMs 



vetcrnus and Valvata led 30 



Sandstone, fissile, brown 5 



Jointed clay, greenisli. Has single bones of sauropods 30 



Sandstone, gray to brown, much cross-bedded with local zones of 

 conglomerates. Small trunks of cycads (Cycadella) occur 



rarely and some of them in their places of growth 10 



Clay, greenish, having toward tlie top the main level for Bronto- 

 saurus and Morosaurus. To the west more and more of these 

 three lowest zones are replaced by sandstones attaining to 125 

 feet 60 



Total 206 



Break in deposition. 

 Jurassic. Sundance formation. Siliceous limestone with Camptonectes 



hellistriatus and Belemnites 1 



Shale, green 4 



Sandstone, green, tliin- and cross-bedded, with Belemnites 2 



Shales, olive green, with lenses of thin sandstones toward the top 

 and an abundance of calcareous concretions below. Near the 

 top, Ostrea strigilecula and 0. densa. Ten feet from top, Cardio- 

 ceras cordiforme is most abundant, along with Pentacrinus 

 asteriscus. Belemnites densus occurs throughout, though rare. 

 About 10 feet above base occur many concretions replete with 

 Astarte paelcardi, Tancredia hulhosa, T. magna, Lima lata, 

 Goniomya montanwnsis, Pleuromya suhcompressa, Cardinia 

 wyomingensis, Cardioceras cordiforme, etcetera. Just above 

 the concretion zone occur the skeletons of Baptanodon and 



plesiosaurs. About 75 



Sandy shale, greenish, with an abundance of Belemnites , 10 



Sandstone, soft, green, and yellowish, weathering into red beds. 



Rippled. Has many Belemnites densus and B. curtus 25 



Sandstone, thin-bedded, white, with green sandy shale partings. 



Has bivalves and Lingula hrevk'ostris 20 



Sandstone, yellowish and thin-bedded 20 



Sandstone, heavy-bedded 20 



Total 177 



Break in deposition. 

 Triassic. Chugwater red beds. 



Dr. S. H. Knight, of the University of Wyoming, has during the past 

 two summers been studying the Morrison and Sundance formations south 

 from the Freezeout Hills to the Colorado State line, and has furnished 

 the writer with the following information. At the north the Sundance 

 has a thickness of 179 feet, and the greenish shales, sandy limestones, 

 and shaly sandstones are more or less fossiliferous to the top of the forma- 



