41 



radials, and entirely within the basal concavity. First primary 

 radials pyramidal, heptagonal and hexagonal. Second primary 

 radials about one-third as large as the first, nearly as long as wide, 

 pentagonal. Third primary radials about the size of the second, hex- 

 agonal, and support on each of two upper sides the secondary radials. 

 Our specimen is slightly injured at the base of the arms, but as near 

 as can be determined there are three secondary radials in each series, 

 the last being axillary and supporting the arms. This gives twenty 

 arms to the species. The arms are composed of a single series of 

 cuneiform plates, each one of which bears a long, strong pinnule. 



In the regular interradial area, shown in the illustration, the first 

 plate is as large as a first primary radial, truncates a subradial, and is 

 followed by two somewhat smaller plates in the second range, two quite 

 small plates in the third range, and one or more in the fourth range. 

 Above the fourth range the plates are not accurately determined. 

 This is evidently a regular interradial area. The other areas and the 

 vault are unknown. 



This species will be readily distinguished from \R. douglass i by 

 being a smaller species, having only twenty arms instead of thirty 

 or more, and by the single series of arm plates instead of a double 

 series. 



Found by Earl Douglass in the Upper Burlington or Lower Keokuk 

 Group, on Bridger Mountains, near Bozeman, Montana, and now in 

 his collection. 



RHODOCRINUS BRIDGERENSIS, n. sp. 



Plate III, fig. 3, side mew. 



Species below medium size. Calyx globular or subspheroidal. No 

 radial ridges. Plates granular, not sculptured. Basal cavity moder- 

 ately deep, column very large, composed of very short pieces. This 

 species has twenty arms. The arms are small. 



This species is distinguished by the globular calyx, large column 

 and small arms. 



Found in the Burlington or Keokuk Group by Earl Douglass, in 

 Bridger Mountains, Montana, and now in his collection. 



