83 



Found by Earl Douglass in the subcarboniferous rocks of 

 Bridger mountains, near Bozeman, Montana, and now in the col- 

 lection of S. A. Miller. 



POTERIOCRINUS DOUGLASSI, n. sp. 



Plate V, Fig. 16, side view, with the azygous area on the right; 

 Fig. 17, same magnified two diameters. The 

 specimen is on a slab. 



Species small. Calyx short, obconoidal, one third wider than 

 high. Plates convex; sutures distinct. Surface granular. Column 

 rather large, round, every alternate plate projecting. 



Baeals form a low cup that is truncated for the column and 

 expanded above. Subradials larger than the basals and nearly 

 as long as wide. First radials as much larger than the subradi- 

 als as the subradials are larger than the basals, wider than long, 

 pentagonal, truncated the entire width above, and separated from 

 the secoDd radials or brachials by a gaping suture. A single, 

 elongated, brachial or second radial, rounded and contracted in 

 the middle, and axillary, supports upon its superior sloping sides, 

 in each radial series, the free arms. The arms do not again bi- 

 furcate, and hence there are ten arms in this species. The arms 

 are composed of very long, slightly constricted plates, that alter- 

 nately project on each side, for the support of coarse, long- 

 jointed pinnules. 



The first azygous plate cannot be seen in our specimen. The 

 second plate is large, truncates a subradial and extends as high 

 as the middle of the first brachial. The plate succeeding it is 

 much smaller; only part of the alternate plate on the right can 

 be seen, but enough is exposed to show the usual alternate ar- 

 rangement that characterizes this genus. 



This species is distinguished by the form of the calyx, single 

 brachials and structure of the arms. While it is not conspicuously 

 marked by any peculiar feature, yet we do not know of any spe- 

 cies with which it might be confounded. 



Found by Earl Douglass, on the Bridger mountains, at Boze- 

 man, Montana, and the name is in honor of the collector. The 

 specimen illustrated is in the collection of S. A. Miller. 



