40 



bears seven arms. The axillary third secondary radial on the right 

 very clearly bears two arms and the axillary third secondary radial 

 adjoining the azygous area bears upon one side an arm and upon the 

 other two plates, the last one being axillary and supporting two arms. 

 It leaves, therefore, two arms to be supported by the middle series of 

 plates. This arrangement may be peculiar to this ray. The righl 

 lateral ray is not fully exposed, as the specimen is on a slab, but it 

 appears to have only six arms, but one appears to follow the plate 

 resting in the angle at the junction of the first secondary radials. 

 The species, therefore, possesses between thirty and thirty-five arms. 

 If the rays were uniform it would possess thirty-five arms, but 

 another specimen on the same slab shows one ray very clearly pos- 

 sessing only six arms. The arms are small and composed of a double 

 series of small interlocking plates that bear strong pinnules. 



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

 first plate truncates a subradial. it is followed by two plates in the 

 second range, three in the third, and three in the fourth, above which 

 they are not disclosed. In the azygous area the first plate is twice 

 as large as the first plate in the regular area and truncates a very 

 large subradial. It is followed by four plates in the form of an arch 

 the middle one of which is as large as the first plate in a regular 

 area. There are also four plates, in the form of an arch, in the 

 third range, the middle one of which is the larger and above these 

 smaller plates graduate up into the vault. 



The vault is not exposed in either of our specimens. 



This is a strongly characterized species, 



Found by Earl Douglass, in whose honor we have proposed the 

 specific name, in the Upper Burlington or Lower Keokuk Group, on 

 Bridger Mountains, near Bozeman, Montana, and now in his collec- 

 tion. 



RHODOCBINUS BOZEM ANEXS1S. 11. sp. 



Plate III, fig, 2, side view. 



Species rather below medium size. Calyx bowl-shaped, radial 

 ridges not defined. Plates sculptured and more or less pyramidal. 

 Basal cavity deep. Column medium size, round, and composed of 

 plates of equal length. 



Basals form a cone within the calyx, into which the end of the col- 

 li mu is inserted. Subradials not any larger than the first primary 



