LOGAN : FREEZE-OUT HILLS OF WYOMING. 



113 



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flXIT 





to the calcareous concretions. From these concre- 

 tions the following forms were obtained: Pinna 

 hingi. Pinna sp., Cardioceras cordiforme, Avicula 

 heedei, Astarte packardi, Pentacrinus aster icus, 

 Tancredia hulhosa, Tancredia magna, Lima lata, 

 Gomomxja montanaensis, Avicula macronatus,Pleu- 

 Tomya suhcompressa, Cardinia Wyoming ensis, Pseu- 

 domonotis curta^ Belemnites densus, and, in the 

 clay, Belemnites curtus. This stratum contains also 

 the remains of plesiosaurs and ichthyosaurs. It is 

 the most abundantly fossiliferous of all the Jurassic 

 strata. It is also one of the most persistent beds, 

 and is everywhere characterized by the great abun- 

 dance of belemnites. 



14. Greenish-colored sandstone, separating 

 into thin layers 2 ft. to 5 ft. 



This stratum contains considerable calcareous mat- 

 ter, is very persistent, and is easily recognized on ac- 

 count of its uniformly greenish color. The following 

 fossils occur in it : Camptonectes hellistriatus, Camp- 

 toncctes extenuatus, Ostrea densa, and Ostrea strig- 

 ilecula. 



15. Purplish clay containing considerable arena- 

 ceous inclusions 40 ft. 



The clay contains, in the lower part, a thin stratum 

 of sandy limestone in which the following fossils were 

 found: Pentacri7ius astericus, Asterias duhium, 

 Pseudomonotis curta, Avicula macronatus, and 

 Ostrea strigilecula. 



The Atla7itasaurus Beds. The last stratum is 

 the last one containing marine fossils, and probably 

 closes the Jura, but some of the non-fossiliferous beds 

 lying above may belong to that formation. The suc- 

 ceeding stratum varies so much in thickness that it 

 may represent the eroded surface of the Jura upon 

 which the Atlantasaurus Beds were deposited. 



16. Fine-grained, grayish-white sand- 

 stone ". 10 ft. to 125 ft. 



The above stratum varies much in thickness within short distances, 

 t one point on the Dyer ranch it has a thickness of only 10 ft., while 

 few miles southeast it reaches a thickness of 125 ft. The sandstone 

 imposing the layer is of nearly uniform color and texture. Its in- 



Qcjt^m. 





'M^MM 





