17 



Found at a place called Chert Hill, in Alabama, supposed to 

 be of the age of the Keokuk Group, and now in the collection of 

 Charles L. Faber. 



DORYORINUS 8AMPSONI, n. Sp. 



Plate III, Fig. 20, azygous side; Fig. 21, opposite view; Fig. 

 22, summit, part of the spines are broken off. 



Species above medium size. Body somewhat urn-ehaped, base 

 expanded, subcylindrical from the base of the third primary 

 radials, and then abruptly expanded horizontally to the free arms, 

 where the body has a subpentagonal outline, and above which the 

 vault is perpendicularly elevated, preserving the subpentagonal 

 outline a distance nearly equal to the height of the calyx and 

 having a nearly flat summit. The expansion of the calyx from the 

 basals to the third radials is less than the expansion of the 

 base itself. The plates are convex or tumid. Ambulacral open- 

 ings directed horizontally and not visible in a basal or summit 

 view. 



Basals the largest plate in the body, constricted in the superior 

 part and broadly flanged below. The |bottom is concave, and 

 columnar canal small. First primary radials a little wider than 

 long, each one bears a transverse central node, three hexagonal, 

 two heptagonal. Second and third primary radials together very 

 little more than half as large as the first. Second primary radials 

 quadrangular, two or three times as wide as high. Third primary 

 radials about the size of the second, three hexagonal, two penta- 

 gonial, curved outward, axillary, and, in the ray on each side of 

 the azygous area bear a single secondary radial, on each outward 

 sloping side, which is directed horizontally and bears upon each 

 outward sloping side a single tertiary radial which gives to each 

 of these rays four arms. In the ray opposite the azygous area, 

 the third primary radial bears upon one outward side two secondary 

 radials and upon the other an axillary secondary radial, which sup- 

 ports upon each outward side a single tertiary radial, which gives 

 to this ray three arms. In each of the lateral rays, the third 

 primary radial bears upon each superior, outward sloping side two 

 secondary radials, which gives to each of these two arms. There 

 are, therefore, fifteen arms in this species. The arm formula 

 is 4 + 2 + 3 + 2 + 4. 

 —3 



