62 



PLATYCRINUS SUBSCITULUS, n. Sp. 



Plate IV, Fig. 12, basal view; Eig. 13, summit view; Eig 14, 

 azygous side; Fig. 15, opposite side. 



Species medium or rather below medium size, calyx and 

 vault subequal, in capacity, and it belongs to the discoid 

 forms. Calyx discoid, subpentagonal, about three times as 

 wide as high. Surface without ornamentation, granular, sutures 

 beveled. 



Basals form a pentagonal disc with a concave depression 

 toward the central part, where the column attached. The 

 bevelei suture surrounding the disc will allow the calyx to 

 rest on the rim of the disc surrounding the concave depres- 

 sion. First radials are directed upw r ard at an angle of about 

 forty -five degrees and are convex toward the facet for the 

 second radials, which is concave and occupies a little more 

 than one-third of the diameter of the plates, and is a little 

 more than half a circle. The second radials are short, con- 

 stricted, directed horizontally and axillary. 



The interradial areas are depressed so as to leave the form 

 pentagonal when seen from above. The interradials are elon- 

 gated, and instead of rising perpendicularly from the calyx 

 are inclined inward so as to contract the vault in the inter- 

 radial areas. 



Vault elevated over the ambulacral canals and depressed in 

 the ambulacral areas so as to leave only a slight convexity 

 centrally. The plates of the vault are subspinous. A large 

 plate is situated subcentrally on the azygous side and sur- 

 rounded with seven plates, six of which are subspinous. The 

 azygous orifice is situated between the ambulacral openings, 

 and the first azygous plate is shorter and smaller than the 

 first regular interradials. The orifice is surrounded by eight 

 plates. 



This species is distinguished by its general form, freedom 

 from surface ornamentation of the calyx, quinquelobate aspect 

 as seen from above, projecting second radials, and the limited 

 number of plates on the vault. 



Found in the Burlington Group, at Sedalia, Missouri, and 

 now in the collection of F. A. Sampson. 



