CERATOPS beds' OF WYOMING AND MONTANA 27 1 



Dinosaur horizon there is a band filled with brackish-water fossils, 

 including Ostrea glabra var. arcuatilis Meek; Anomia micronema 

 Meek; Corhula undifcra Meek, and Modiola sp. The greater num- 

 ber of the Black Buttes invertebrates, however, have been obtained 

 from strata some 40 or 50 feet higher, and consequently a little above 

 the Dinosaur bed. Here there is a band which in some places is about 

 four feet thick, almost wholly made up of shells. By far the most 

 abundant species is Corhicula fracta Meek, and immediately associ- 

 ated with it are Corhicula occidentalis M. & H.; Neritina haptista 

 White; N. volvillneata White, and Melania wyomingensis Meek, all 

 of which probably lived in slightly brackish water, for this species of 

 Melania has almost invariably been found associated with brackish 

 water or marine forms, although it is referred to a fresh-water genus. 

 At the base of this shell bed and immediately above a coal seam Unto 

 shells are abundant. These purely fresh-water forms are found on the 

 slope mingled with the Corhicula shells, but all that were found in situ 

 were either at the base of or a few feet above the Corhicula bed. 



The Unione fauna is strikingly like that of the Ceratops beds in 

 Converse County, as the following list of species will show: 



Unio couesi White 

 Unio propheticus White 

 Unio aldrichi White 

 Unio proavitus White 

 Unio holme sianus White 

 Unio endlichi White 

 Unio crypiorhynchus White 

 Unio hrachyopisthus White 

 Unio goniambonaius White 

 Unio dance M. & H. 



Immediately above the Corhicula bed a band is locally filled with 

 Tulotoma thompsoni and occasional Unios, and it is overlain by shales 

 containing Ostrea and Anomia in the lower part and the following 

 species above: 



Unio couesi White 

 Corbula undifera Meek 

 Corbula subtrigonalis M. & H. 

 Cassiopella turricula White 

 Goniobasis gracilenta M. & H. ( ?) 

 Viviparus plicapressus White 

 Campeloma vettda M. & H. 

 Campeloma multilineata M. & H. 



The fossil plants of Black Buttes, ranging through the same strata 

 as the invertebrates and extending up a few feet higher to the bed just 

 above the principal coal, are as follows: 



Proc, Wash Acad. Sci., August, 1909. 



