10 ' PROCEEDINGS OF THE NATIONAL MUSEUM vol. 74 



the posterior interradius are hexagonal in outline. The latter two 

 are heptagonal. The r. post. B supports RA on its upper left 

 ■shoulder. The post. B supports RA on its upper right shoulder and 

 X on its superior face. On one specimen where the surface is some- 

 what better preserved than usual there are obscure radiating ridges 

 passing over to the adjacent plates. The centers of the basals are 

 elevated, the surface sloping gently to the upper and lower margins 

 and much more abruptly to the sides. This results in well-defined 

 depressions along the interbasal sutures. Low, broad ridges pass over 

 to the radials, outlining these depressions. The radials vary con- 

 siderably among themselves in size. The arm facets are large and in 

 the adult specimens are nearly vertical in attitude or are inclined 

 very slightly upward. The amount of inclination varies in different 

 rays. In the young specimen 3& the upward inclination is somewhat 

 more pronounced but not greatly so. The radial is pierced by an 

 axial canal separate from the food-grove. On the surface of the 

 arm facet to either side of the axial canal lies a short horizontally 

 disposed articular facet. The surface of these facets is roughened by 

 short vermicular ridges. The upper portion of the radial curves 

 over and inward, forming a platform of appreciable width. Thus 

 the radials from the exterior appear to be massive plates, whereas 

 when cleared from the matrix they are found to be relatively thin. 

 In the posterior interradius there are three anal plates within the cup. 

 The radianal is fairly large, pentagonal, resting below on the post. 

 and r. post. BB, laterally abutting on r. post. R and x and supporting 

 rt above. Anal x is somewhat larger than RA and supports two tube 

 plates. It abuts laterally on 1. post. R, RA, and rt, while below it 

 rests on the post. B. The plates of the posterior interradius are 

 traversed by radiating ridges that are really folds in the plates. 

 These progressively become stronger as the tube proper is approached. 

 Outside the proximal tube plates nothing is known of the structure 

 of the tegmen. Specimen 36 has one arm ossicle lying approxi- 

 mately in place. It is short and heavy and is pierced by an axial 

 canal. On either side of the canal is a short articular facet, similar 

 to those present on the main arm facet. 



Horizon and locality. — Lyon cites his type specimen as from the 

 quarries on Beargrass Creek, near Louisville, Ky. This would un- 

 doubtedly place the horizon as Onondaga (the Jeffersonville lime- 

 stone of present local usage) of the Middle Devonian. 



VASOCRINUS SCULPTUS Lyon 



Of this, the second of Lyon's original species, a fair amount of 

 material is now available for study. There are five dorsal cups in 

 an excellent state of preservation. Three of these have the tegmens 

 partially preserved, one has a fragment of column attached and two 



