FOSSILS OF THE CARBONIFEEOUS. 



225 



LAMELLIBRANCHIATA. 



The occurrence of a number of species of this class in the Carbonifer- 

 ous Group, in the region of the Rocky Mountains, is unusual, as heretofore 

 it has been but sparingly represented. 



In 1852 Prof. J. Hall (Stansbury's Expedition to the Great Salt Lake, 

 p. 412) described a few species, viz: Avicula^Pseudomonotis curta, Tellino- 

 mya protensa (probably belongs to the genus Modiomorpha), Allorisma 

 terminalis, Cypricardia occidentalis, Nucula arata. 



Of these the last three species were obtained from Eastern Nebraska or 

 the Mississippi Valley region. To the first two may be added twenty-two 

 species mentioned by different authors: 



Marcou, J., 1858. Geology of North America, p. 44. Myalina Apachesi. 



Meek, F. B., 1860. Preliminary Notice. 1876. Report Explorations Across the Great 

 Basin of Utah, Simpson, p. 354. Aviculopecten UtaJiensis. 



White, C. A., 1874. Preliminary Notice. 1875. Explorations and Surveys West of 

 the 100th Meridian, vol. iv, pt. 1, p. 146. Aviculopecten occidentalis, A. Corey- 

 anus, A. McCoyi, A. f interlineatus, Pinna peracuta? , Monopteria Marian, My- 

 alina, sp., M. f Sicallovi, Balcevellia parva, Schizodus Wheeleri, Allorisma 

 subcuneata, var. Also, in Appendix to Supplement of vol. iii of the same 

 Survey, 1881, p. xxv. Myalina Permiana and Pleurophorus subcostatus. 



Whitfield, R. P., 1875. Carroll, Montana, to Yellowstone National Park, Ludlow, p. 

 143. Pinna Ludlovi. 



Meek, F. B., 1877. Geological Exploration of the Fortieth Parallel, vol. iv, p. 96. A. 

 occidaneus. 



Two other species are described as from the Carboniferous, but they 

 are more properly referred to the Devonian by Messrs. Hall and Whitfield. 



Hall, J., and Whitfield, R. P., 1877. Geological Exploration of the Fortieth Parallel, vol. 

 iv, p. 273. Aviculopecten Webcrensis, A. curto-cardinalis, A. parvulus, Mya- 

 lina aviculoides, M. Permiana, SedgwicTcia f concava, Cardiomorpha Missou- 

 riensis. 



The latter species, Cardiomorpha Missouriensis, although described from 

 the Coal Measures of Missouri and Illinois, is, in Nevada, found in the strata 

 at the summit of the Devonian and is not, there, a Carboniferous species; 

 with this exception, all of the twenty-four species heretofore described are 

 from the upper portions of the Carboniferous Group, usually referred by 

 authors to the Coal Measures. From the latter horizon but one species is 

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