28 



BLAIROCRINUS SPINOSULXJ8, n. Sp. 



Plate VII, Fig. 16, azygous view; Fig. 17, view opposite the 

 azygous area; Fig. 18, summit view. 



Calyx truncated at the base, obpyramidal, about twice as wide 

 as higli; plates sculptured; radial ridges rather sharp; inter- 

 radial area flat; secondary radials and arm openings directed 

 horizontally. 



Basals three, forming a low, ircegular, subhexagonal disc, 

 nearly covered below by a round column, which is attached to 

 the basals, by radiating denticulations. Columnar canal rather 

 large, pentalobate. The little rim formed by the basals bears a 

 node or short ridge directed toward each adjoining plate above. 

 First primary radials the larger plates of the calyx, wider than 

 high, three hexagonal, two heptagoual, convex in the central 

 part, and sunken at the angles so as to leave a shoi-t ridge 

 directed toward the center of each adjoining plate. Second pri- 

 mary radials quadrangular, about twice as wide as high, and 

 similarly sculptured, though the radial ridge is much stronger 

 than the transverse one. Third primary radials about the same 

 size as the second, pentagonal, axillary, and bearing upon each 

 upper sloping side two secondary radials, While there are only 

 ten secondary radial series, there are two arm openings over 

 each series, indicating that the arms, at once, bifurcated on be- 

 coming free. 



Regular interradials three, one hexagonal plate resting between 

 the upper sloping sides of the first primary- radials and followed 

 by two smaller elongated plates, that separate the secondary 

 radials and connect with the plates of the vault. The first 

 azygous plate is in line with the first primary i-adials, of about 

 the same size, and sculptured in like manner, it is followed by 

 two plates, in the second range, and three in the third range, 

 which separate the secondary radials and connect with the plates 

 of the vault. 



The vault is strongly pentalobate, by reason of the horizon- 

 tally projecting secondary radials extending beyond the upper 

 part of the interradial areas. It is elevated over the arm open- 

 ings, and gently convex toward the center. There is a spinous 

 plate over each double arm opening, and between these spinous 

 plates, in each radial series, there is a rather large plate, that 



