Descriptions of New Crinoids. 245 



DESClilPTlON'S UF NEW CRINOIDS FR03I THE CIN- 

 CINNATI GROUP OF THE LOWER SILURIAN AND 

 THE SUBCABBONIFEROUS OF KENTUCKY. 



Bj' A. G. Wetherby, A. M., 

 Prof, of Geology and Zoology, University of Cincinnati. 



Glyptoorinus richardsoni, nov. sp. 



Plate XVI., fig. 1, azygos side; la, portion of ray enlarged, showing fixed pinnulse. 



Under hasals — Not developed, or so slightly as not to be character- 

 ized. 



Basals — Five, pentagonal, wider than high, and so arranged as to 

 alternate with the first radials, the center of which is coulinuons with 

 their line of junction. In none of the specimens studied are these 

 plates sufficiently well shown to indicate anything in addition to what 

 is here given. 



Radials — First series five, pentagonal, somewliat higher than wide, 

 the lower extremity resting between the upper faces of contiguous 

 basals. Each of these plates has a much elevated central portion, of 

 the same general form as the plate itself, from the lower part of 

 which the thinner articulating edges project. 



Second series five, hexagonal, higher than wide, and resting squarely 

 upon the upper side of -the first radials. These plates, also, have a 

 raised central portion, quadrangular in form, from which the lateral 

 articulating edges project at a much lower level. 



Third or axillary series five, hexagonal, higher than wide, and rest- 

 ing upon the upper face of the second series. These plates, also, have 

 the raised central area, which is slightly depressed at the line of junc- 

 tion of the two upper articulating surfaces, giving this extremity a 

 bifurcate appearance at first glance. Upon this series of radials the 

 first division of the rays takes place. The only one of which all subse- 

 quent subdivisions are clearl}^ shown, is that figured on the right side of 

 the azygos area. The branches of this ra}^, after the first bifurcation, 

 take a very diff"ereut course. The one upon the right divides but once 

 more, and tliat is about the fiftieth plate above. The left hand 

 branch, or that next to the az3'gos side, first divides upon the sixth 

 plate above, and each of these branches again upon the fiftieth (?) 

 plate above this. There thus result from the subdivisions of this ray 

 six arms at the free extremit}'. If this is the arrangement for each of 

 the five rays, the number of free arms is thirty. As in the other 



