28 



Family GLYPTOCRINID.E. 



GLYPTOCRINUS MERCERENSIS, n. Sp. 



Plate II, Fig. 23, azygous side view. 



General form of the calyx, somewhat obpyramidal, transverse sec- 

 tion pentagonal. Radial ridges prominent, plates deeply sculptured 

 with stellate ornamentation. Interradial areas flattened. Column 

 round and medium size. 



There are five sculptured basal plates that extend in the form 

 of a sharp ring below the top of the column. They are a little 

 wider than high. The first primary radials are heptagonal, rather 

 wider than high. The second primary radials are hexagonal, longer 

 than wide and about two-thirds as large as the first. The third 

 primary radials are heptagonal, abut upon two interradials, at each 

 side, wider than high, about two-thirds as large as the second, 

 axillary, and bear upon the superior sloping sides the secondary 

 radials. There are three or four secondary radials in each series 

 that enter into and form part of the calyx and then the radial 

 ridge becomes more prominent and the arms become free. There 

 are no tertiary radials and no divisions of the arms. There are, 

 therefore, only ten arms in this species. The plates of the arms 

 are short and the pinnules very dense. 



The regular interradial areas have one large plate in each, rest- 

 ing upon the upper sloping sides of the first primary radials and 

 separating the second primary radials. It is followed by two plates 

 in the second range and above this the number cannot be ascer- 

 tained from our specimens. In the azygous interradial area there 

 is one large plate resting upon two first primary radials, which is 

 followed by three plates in the second range, and above these the 

 number of plates can not be determined in our specimens. A ridge 

 arises at the center of the first azygous plate and extends straight 

 up the center of the azygous area, a distance beyond the com- 

 mencement of the free arms, and to the top of a proboscis. This 

 species possesses a vault altogether different from that belonging 

 to G. decadactylus, and it also possesses a proboscis or extension 

 of the vault which has not been heretofore known to belong to any 

 species of Glyptocrinus. In the region of the first and second 



