77 



PLATYCRINUS SEMIFUSUS, n. Sp. 



Plate IV, Fig. 41, side view, Fig. 42, basal view. 



This species is founded upon two casts, but the specimens 

 are in a fine state of preservation, and the ornamentation, we 

 presume, indicates the ornamentation of the test. The species 

 is above medium size. The calyx is pointed below, subpen- 

 tagonal from the basals upward and constricted below and at 

 the second radials, so as to destroy the subpentagonal outline. 

 The heigth is a little more than the diameter and if the test 

 were preserved the heigth would still be more than the diame- 

 ter. The shape is half fusiform. The surface is ornamented 

 with rounded ridges that radiate downward from the second 

 radials to the base of the first radials and then contract to 

 the pointed base below, and these ridges bear very fine longi- 

 tudinal lines; or we might say the specimens are ornamented 

 with longitudinal, low, fusiform ridges, that are longitudinally 

 marked with very fine lines. 



Basals form a cup, pentagonal above and pointed below, and 

 having a diameter equal to about two and a half times the 

 height. The first radials have a length greater than the width 

 and have nearly parallel sides. The facets for the articulation 

 of the second radials are very small. The vault is unknown. 



The general form will distinguish this species from all others, 

 beside, the surface ornamentation is quite peculiar. 



Pound by R. A. Blair in the chert belonging to the Burling- 

 ton Group, at Sedalia, Missouri, and now in the collection of 

 S. A. Miller. 



PLATYCRINUS MODESTUS, n. Sp. 



Plate IV, Fig. 43, side view; Fig. 44, basal view; Fig. 45, Summit 

 view, of the same specimen. 



We have several specimens of this species, but they are all 

 casts. The species is below medium size. The calyx is bowl- 

 shaped, pentagonal, and about one third wider than high. It 

 is constricted below the arms. There are no indications of 

 any ornamentation. 



Basals form a nearly flat, pentagonal disc. The first radials 

 have a width a little greater than the length and they expand 

 moderately upward. The superior angles are strongly truncated 



