132 CARBONIFEROUS PERIOD. 



surface marked by fine stria3 of growth, but no radiating striae have been 

 detected. 



Length, twenty-five millimeters ; breadth, twenty-six millimeters ; 

 height, seventeen millimeters. 



The only American shell likely to be confounded with this species is 

 B. Missouriensis Shumard, but it differs somewhat in outline and propor- 

 tions as given in the description and figures of Dr. Shumard and also in the 

 character of the plications. There is a shell in the Kinderhook fonnation 

 at and in the vicinity of Burlington, Iowa, which is usually referred to B. 

 Missotiriensis. If that shell is coiTcctlysSO referred, it diflfers mateiially from 

 B. Bochjmontana in being plainly marked by numerous distinct, radiating 

 stria3 upon both valves. This shell is also very closely like B. remformis 

 Sowerby from the Carboniferous strata of England, and may possibly be 

 identical with it. 



■ Position and locality. — Strata of the Carboniferous period ; near Beck- 

 with Spring, Cedar range, Utah. Professor Marcou obtained his type- 

 specimens from Pecos Village, New Mexico, where he found them associated 

 with Froclmtus semireticulatus and Spirigera siibtilita. 



■ Family SPIRIFERIDiE. 



Genus SPIRIFEE SOWERBY, 1S15. 

 Spirifer cameratus Morton. 



. Plate X, fig. 1 n, b, c, aud d. 



Spirifer cameratus Morton, 1836, American .Journal Science, xxix, 150. 

 Spirifer tripKcatus Hall, 1852, Stansbury's Expedition Great Salt Lake, 410. 

 Spirifer Meusehaclianus Eoenier, 1852, Kreidebildnug von Texas, 88. 

 Spirifer cameratus Hall, 1850, Pacific Railroad Surveys, iii, 102. 

 Spirifer cameratus Hall, 1858, Geology of Iowa, i, pt. ii, 709. 

 Spirifer cameratus Meek, 1872, U. S. Geol. Surv. Nebraska, 183. 



Shell usually of medium size, but sometimes quite large, subsemicir- 

 cular or subtrihedral in outline, almost always broadest at the hinge-line ; 

 the hinge-extremities often pointed and sometimes mucronate. 



Dorsal valve not quite so capacious as the other ; mesial fold distinct, 

 broad at the front, sometimes sharply elevated, but more commonly rounded, 

 clearly defined from front to beak, and rapidl}^ increasing in width to the 



