NORTH AMERICA AND THEIR VERTEBRATE FAUNA. 69 



the conditions in northern Colorado. This has been made under 'Formation 

 names.' Barton's Tensleep in Colorado is probably in part equivalent to the sand- 

 stone-limestone series; that is, the Ingleside series. 



"Owing to the absence of fossil evidence in the Badito formation, and from the 

 fact that it is separated so widely from any recognized Fountain exposures, it has 

 not been definitely correlated with the Fountain. Lithologically they are very simi- 

 lar, and the Badito overHes pre-Cambrian rocks unconformably, bearing about the 

 same relation to the overlying formations as does the Fountain. On these grounds 

 they are at least approximately in the same horizon. 



"The Cutler formation is defined as that portion of the 'Red Beds ' lying above 

 the Rico, where that is present, or otherwise as succeeding the Hermosa and below 

 the Dolores. The Cutler is assigned to the Permian purely on stratigraphic grounds, 

 and is separated from the Rico by a purely arbitrary line. There seems to be as 

 good ground for assigning the Lykins, above the crinkled sandstone, or at least the 

 lower portion of it, to the Permian, and thus correlating it with the Cutler. 



" Above the Cutler formation in the San Juan region is a series of sandstones, 

 sandy shales and conglomerates which vary in thickness from 800 to 400 feet, and 

 from that down to 30 feet at the San Miguel River, disappearing entirely north of 

 this river. These shales and sandstones are a bright vermiHon in color, and are 

 known as the Dolores formation. They are assigned to the Triassic age because of 

 the scanty, but widespread, vertebrate, invertebrate, and plant remains. The ex- 

 treme upper part of the Lykins in Larimer County may be equivalent to the Dolores 

 and thus be Triassic. If so, it is impossible to draw a line between the Permian and 

 Triassic in eastern Colorado." 



The following fossils were obtained by Mr. Butters from the Lykins 

 formation : 



Lower horizon : Myalina subquadrata, Bellerophon crassus. 



Upper horizon (identified by Dr. Girty) : Myalina wyomingensis, Myalina 



perattenuata, Alula squamulifera, Alula gilberti (?), Pleurophorus sp., 



Murchisonia. 



"Of the Lykins fossils all except Alula squamulifera and Murchisonia butter si, 

 which are new species, and Alula gilberti (?) are found in the Rico formation of the 

 San Juan region. Girty reports about 3 7 species from the Rico. Of these Bellerophon 

 crassus and Myalina subquadrata and others also occur in the Hermosa. It will be 

 noticed by the list of the Lykins fossils that these two occur at a different and a 

 lower horizon in the Lykins than the remainder. This rather strengthens the corre- 

 lation of the Lykins with the Rico. Bellerophon crassus and Myalina subquadrata 

 are found in the Hermosa and other Pennsylvanian horizons lower than the Rico. 

 Pleurophorus subcostatus and Pleurophorus occidentalis occur in several localities, 

 but it is by no means certain that the Pleurophorus of the Lykins belongs to either 

 one of these species. A doubtful identification of Myalina wyomingensis has been 

 made from Leadville. With these possible exceptions none of the Lykins fossils 

 have been reported by Girty from any formations in Colorado other than the Rico. 

 In summarizing it will be seen that there is fairly good evidence for correlating the 

 Lykins with the Rico, and no evidence for correlating it with any other horizon. The 

 Lykins fossils were collected from locahties a long distance apart — from the extreme 

 northern part of Larimer County in the north to Perry Park in El Paso County in 

 central Colorado — so that the Lykins appears to be more widely distributed than 

 the Rico." 



