No. 9. — New Blastoids and Brachiopods from the Rocky Mountains. 



By Thomas H. Clark. 



Bl.\stoidea. 



Blastoids are so rare in the Rocky Mountains that the discovery 

 of new species of these fossils in that region is of considerable interest 

 and importance. In 1915, while a member of the Harvard Summer 

 School of Geology, I was fortunate enough to find several specimens 

 belonging to Pentremites and Schizoblastus in the Carboniferous 

 limestone of southwestern Montana. The discovery of these fossils 

 here is important from another point of view, namely, that the Pen- 

 tremites were collected from that part of the Carboniferous limestone 

 which must be acknowledged to be of Pennsylvanian age. The 

 specimens of Schizoblastus and one Pentremites came from Squaw 

 Creek, ofT the West Gallatin River, and the other Pentremites were 

 collected at Old Baldy, near Virginia City, Montana. 



At Old Baldy, there is an exposure of Carboniferous limestone, the 

 greater part of which contains fossils characteristic of the Madison 

 formation (Mississippian). The limestone is capped by the Quadrant 

 quartzite, which is recognized as Upper Carboniferous. Immediately 

 below the quartzite there is a considerable thickness of limestone 

 which contains Pennsylvanian fossils. Schuchert, in 1910, writing 

 of the Old Baldy fossils stated that "in the light of the Arkansas 

 (Morrow formation) collections, these fossils must now be referred to 

 the Pottsvillian " (Bull. Geol. soc. Amer., 20, p. 426-606). 



Since 1873, when Meek published his lists of fossils collected from 

 the rocks of Montana (Meek, Rept. U. S. geol. surv. Montana Idaho, 

 Wyoming, Utah, 1873, p. 463-478), nothing has been published 

 concerning Pentremites in the Rocky Mountains, and Meek was 

 the first to discover this genus west of Iowa and Missouri. In the 

 report referred to above the occurrence of the following five spe- 

 cies is noted: — Pentremites conoideus, Pentremites subconoidens, 

 Pentremites sijmmctricus, Pentremites (jodonif, Pentremifefi hrad!ei/i. 

 These come from two localities in Montana. In 1905, Mr. Earl 

 Douglass found a specimen at Old Baldy, which was identified by 

 Dr. P. E. Raymond as Pentremites conoideus, and the description of 

 which appears in this paper for the first time. The discovery by the 

 writer of three new species of Pentremites adds considerably to the 



