86 



Family PLATYCBINHm 



PLATYCRINUS DOUGLASSI, n. sp. 



Plate V, Fig. 18, side view; Fig. 19, same magnified two diam- 

 eters. The specimen is compressed so as to appear wider 

 than it really is. 



Species medium or below medium size and belonging to the 

 round, bowl-shaped forms. Calyx round, bowl- shaped, truncated 

 below, and, when not compressed, about as high as wide. Sutures 

 are not beveled. There is a constriction just above the base so 

 as to form a basal rim. The surface is furrowed transversely 

 across the sutures between the first radials and longitudinally from 

 tbe lower part of the facet for the second radials across the basal 

 plate, but increasing in number, so as to cover the basal plates to 

 the constriction above the basal rim. These furrows do not cross 

 each other. The column is small and elliptical. 



Basals form a low cup rather more than one-third the height 

 of the calyx. First radials longer than wide and increasing in 

 width very slowly in their upward extension, so that the calyx in- 

 creases in width very little above the basals. Articulating facets 

 for the second radials very slightly excavated, about one third the 

 width of the plates. Second radials very short or transversely 

 almost linear. Third radials short, axillary, and bear, upon each 

 upper sloping side, the free arms. There are, therefore, ten arms 

 in this species. The arms are long, slender, composed of pro- 

 jecting, cuneiform plates, bearing pinnules alternately. The pin- 

 nules are long and very dense. Our specimen is on a slab and 

 there are fragments of the arms not illustrated, which show the 

 unusual density of the pinnules. 



The superior face of the first radials is transverse, without 

 showing any evidence of interradials. Vault unknown. 



This is a peculiar spfcies, distinguished by its form and surface 

 ornamentation from all others. 



It was found by Earl Douglass, in whose honor we have pro- 

 posed the specific name, on Bridger Mountains, near Bozemau, 

 Montana, and now in the collection of S. A. Miller. The rocks 

 from which it was collected are subcarboniferous. 



