2H8 CAHUdXlKKRoUS KdUM AI'K )NS AND KAI'NAS IIK ('( )I,( >liA IX I. 



Till' t'luiiia of llic \\'('l)<'r roniiution. witli ils Fiisuliii;is :iriil otlicr siiocie.s, i.s 

 ili'iuly of Tppcr Carbon ifiM-ous ngv. Without a sharp break bctwcoi) the upper and 

 lower faunas tliere is yet a certain distinct laclc of ayi'eeinent. Tiie Web(^r formation 

 has a total of 21 species and th(> ^laroon a total of liS species, yet they have only 8 

 species ill ronmiiin. The siunt' facts can be expressed in a ditferent and somewhat 

 less relative niaiinei'. Tlie two foi-niations have a condjined fauna of 41 diii'erent 

 .species. Of these, S are common, and 'dH peculiar to one formation or the other. 

 The fraction -/)-, or the pereentag;e 19.51, may be taken a.s expressing in a general 

 way the degree of affinity of the two faunas. This, however, fails in accurac}', for in 

 the case of species common to both formations no account is taken of instances of 8 

 and 5 occurrences in one. balanced by only 1 in the other. Such faunal peculiarities as 

 exist are bi'ought out so clearly' by the table that it seems hardly necessary to indicate 

 them here. It may be remarked, howevei'. that the cchinoids are not present in 

 the Maroon conglomerate, nor any of the Mollusca, save only 1 .species, in the Weber 

 limestone, and that Productm infiatus, Margini/era lasallensinf , M. ingrata, Spirif^ 

 rocJii/itioiitainis, und SpirlferinacaDijpestris are nearly or quite peculiar to the Weber, 

 and Chonetcs m.esolohus, Productus semireticulatus var. hermosanus, P. cor^a, Mav- 

 glnlfera ■muricata, Spirifei' camei^attis, Scp.mmida/ria perj)leooa, Spi.riferina Icentucky- 

 ensis, Semimda iiid)tlllta, Ilmtedia inormoni, and Puguax ufah to the Maroon. 



In working over these collections my attention was attracted to the circumstance 

 that the large Producti and the smaller species, chiefly belonging to the genus 

 Margiiiifera , seldom appeared in the same local assemblage. In some instances, 

 however, the Marginiferae and the large Producti do so occur, and in the case of 

 stations 2312 and 2313 the two types were found stratigraphically within 10 feet of 

 each other. The selective agencj', therefore, whether stratigraphic or environmental, 

 was not unvarying in its action. 



Mention is made in the Anthracite-Crested Butte folio of the occurrence of 

 Upper Carboniferous fossils in pebbles of the Maroon conglomerates. The collec- 

 tion from station 2306 seems to be an instance of this. The fauna consists of 

 Chietetes rniUeporaceus, Prodtictus cora, Marginifera wahashensiis \'ar., Sijunmidaria 

 perjyleoKi^ Semimda suhtilita^ and Ilustedia morrtioni, and it is surprising to note that 

 its affinities are distinctly with the other indigenous faunas of the Maroon, and not 

 with those of the Weber formation or of the Leadville limestone. 



Collections from three stations not made in connection with the areal work of 

 the Crested Butte quadrangle are included in the table. These are stations 221:4, 

 2245, and 2280. The collection from station 2244, which is on Rock Creek, was 

 made by J. J. Stevenson, and probably is from the horizon of bed No. 1 in his Rock 

 Creek section." A considerable fauna is cited by Stevenson as occurring in this bed. 



a U. S. Geog. Geol. Siirv. W. 100th Mer., Kept., Vul. Ill, p. 362. 



