186 abstracts: geology 



and a considerable area of them is mapped in a stratigraphic paper by 

 C. M. Bauer, who recognizes in them three formations, the Fruitland 

 formation containing all the coal beds at the base, the Kirtland shale 

 in the middle, and the Ojo Alamo sandstone at the top. The inverte- 

 brates, which form the subject of the present paper, nearly all come 

 from the Fruitland formation. 



The list of species shows that the nonmarine invertebrates of the 

 Fruitland formation include both a fresh-water fauna and a brackish- 

 water fauna. The fresh-water fauna is especially notable for the 

 greatly varied development of the genus Unio and for the abundance 

 and considerable variety of the gastropods. The invertebrate evidence 

 as a whole favors the assignment of the Fruitland formation to an 

 epoch considerably later than Mesaverde and Judith River, and possi- 

 bly somewhat earlier than Lance. The Fruitland can hardly be older 

 than Fox Hills, and the sequence from the base of the Fruitland up 

 to the top of the Ojo Alamo, which is conformable, may include the 

 equivalents of everything from the Fox Hills to the Lance inclusive. 



R. W. S. 



GEOLOGY. — Contributions to the geology and paleontology of San Juan 

 County, New Mexico. 4- Flora of the Fruitland and Kirtland for- 

 mations. F. H. Knowlton. U. S. Geological Survey Professional 

 Paper 98-S. Pp. 327-353, with 8 plates and figures. 1916. 

 The object of the present study is to ascertain the bearing of the 

 fossil plants on the age of the series of coal-bearing and related rocks 

 in San Juan basin, New Mexico. A brief historical setting for the 

 geologic facts is given. The material on which the present report is 

 based comprises 20 collections, of which 15 are from the Fruitland for- 

 mation, 3 from the Kirtland shale, and only 1 from the Ojo Alamo 

 sandstone. The bulk of the material comes from the lower or coal- 

 bearing portion of the section, and much of this is preserved on a red 

 baked shale, indicating proximity to coal. Of the 40 forms making up 

 the known flora of the Fruitland and Kirtland formations, 16 have been 

 found in other areas, and the list of these forms brings out the fact 

 that no less than 15 are known to occur in the Montana. A further 

 analysis of the list shows that 12 of the 15 forms occur in the Vermejo 

 formation of Colorado and New Mexico, 10 occur in the Mesaverde, or 

 rocks of about this age, in Wyoming and elsewhere, and 6 species are 

 common to both these areas. On the basis of this showing the con- 

 clusion that the Fruitland and Kirtland formations are of Montana age, 

 seems justified. R. W. S. 



