NO. 24 PTARMIGANIA STRATA — RESSER 1 3 



of the formation. The species are Glossopleura prona, G. arrecta, and 

 Alokistocare globatum. 



Locality 55q. This collection was secured near the top of the 

 Langston formation. The species are : Glossopleura prona, G. arrecta, 

 Kootcnia pcctenoides and Prosacanthoides sp., and Clavaspidella sp. 



It is possible, as Deiss contends, that these fossils do not represent 

 the Ptarmigania fauna, but since they occur directly beneath the 

 shale which contains Spence forms, they are described. It will be 

 observed that these species do not require exclusion of the Langston 

 fauna from the Ptarmigania zone. This question is discussed more 

 fully subsequently. 



Mill Creek, west of Liberty. — Mill Creek was known as Liberty 

 Creek in 1906. Walcott's references to Spence Gulch mentions 

 "Danish Flat," which now is Copenhagen Basin. Spence Gulch is not 

 shown on the Preston or Montpelier quadrangle maps, but evidently 

 is the stream coming into Mill Creek from the west, possibly in 

 sections 10, 2, 3, T. 13 S., R. 42 E., of the Preston quadrangle. 



The Middle Cambrian portion of Walcott's section on Mill Creek is 

 as follows : 



Nounan formation: 



Dolomite. Massive-bedded, passing into bluish-gray, rough, Feet 



weathering dolomite 450 



Quartzite. Gray quartzitic rock 92 



Dolomite and limestone. Dirty-gray calcareous beds, with fossils 272 



Total 814 



Bloomington formation : 



Limestone. Bluish-gray limestone, in alternating massive and 

 thin beds 3^5 



Shale and limestone. Greenish argillaceous shale and thin- 

 bedded limestone, with oboloid brachiopods 575 



Limestone. Thin- and thick-bedded, bluish-gray limestone, with 

 fossils at top and near the middle ; 202 



Total 1. 162 



Blacksmith dolomite: 



Gray dolomite 2 3 



Thin-bedded, bluish-gray dolomite 335 



Total 358 



