EPICONTINENTAL SEA OF JURASSIC AGE 249 
Freeze-Outs. The beds have the same lithological character- 
istics, being composed of sandstones, arenaceous clays, marls 
and impure limestones. They rest on the Red Beds and are 
overlain by about the same thickness of the Como (Atlanta- 
saurus) beds. The latter formation is capped by an apparent 
continuation of the same quartzitic layer which forms the surface 
stratum in the Freeze-Outs. From this area the following spe- 
cies have been determined by the writer and others: Asterias 
dubium, Pentacrinus astericus; Belemnites densus; Cardioceras? 
cordiforme; Pseudomonotis curta; Camptonectes bellistriatus; Ostrea 
strigilecula; Ostrea comoensis; Pinna kingi; Tancredia inornata; 
Pleuromya subcompressa; Astarte packardi; and Goniomya montan- 
aensts. 
Rawlins Peak.—The Jurassic at this point exhibits about the 
same thickness and lithological characters as that of the Como 
area. The beds contain the following forms: Camptonectes bel- 
histriatus ; Belemnites densus,; Astarte packardi; Pseudomonotis curta ; 
Ostrea strigilecula; and Pentacrinus astericus. 
Sweetwater.—In the Sweetwater Drainage area Endlich * gives 
300 feet as the thickness of the jura at that place and states that 
it contains a Gryphea and a Belemnites. 
East of the Wind River Range according to the same writer? 
the Jura has a thickness of 200 or 220 feet and consists at the 
base of dark calcareous shales, covered by beds of dark blue lime- 
stones. These are followed by yellow shales and marls with 
intercalations of thin sandstone layers. Yellow, pink and green- 
ish marls close the section. The fossils obtained are species of 
Belemnites, Gryphea, Rhynchonella, Lingula, Modiola, Pecten, and 
others. 
THE SOUTHEASTERN IDAHO AREA 
In this area St. John3 places the thickness of the Jura at 
2000 feet. Since, however, only the lowermost beds are fossil- 
iferous it is probable that the Jura should be restricted to that 
*Ann. Rep. U. S. Geol. Surv.; Vol. XI, 1877, p. 108. 
2 (bid. p. 87. 
3Ann. Rep. U.S. Geol. Surv., Vol. XI, 1877, p. 495. 
