79 



Vault elevated, the first intorradials standing nearly upright. 

 There are a few large spines on the summit of the specimen, 

 but as the outlines of the plates cannot be determined it is not 

 certain that the spines belong to it, probably they belong to 

 foreign matter. 



This species is distinguished from P. cequiiernus, which it 

 most resembles, by the form of the basals as well as by the 

 proportion of the height to the diameter. The facets for the 

 second radials are also somewhat different, and the angles for 

 the interradials are more obtuse in that species than in this, 

 which shows that the vaults are different, though unknown 

 beyond those plates. It might also be compared with P. pet- 

 tisensis, from which it may be distinguished by the form of 

 the basal cup and the articulating facets for the second radials, 

 and by minor details. 



Found by Mr. F. A. Sampson in the Chouteau Group, at Se- 

 dalia, Missouri, and now in his collection. 



Family PISOCRINIDjE. 



PISOCRINUS BACCULA, n. Sp. 



Plate V, Fig. 23, side view showing 1he small single radial; Fir. 

 24, side view showing the large radial; Fig. 25, baial 

 view; Fig. 26, summit view of calyx. 

 Species large, quite as large as P. campana. Calyx some- 

 what bell-shaped or like a huckleberry; greatest diameter at 

 the lower third and below the point of the small radial; 

 abruptly rounded below and deeply concave or sunken at the 

 columnar pit; rapidly contracted in the upper part. The speci- 

 men illustrated is not round, as seen from below, and all three 

 of the specimens examined seem to be somewhat irregular in 

 this respect, though each of the others is more nearly round 

 and regular than the one illustrated. Plates thick. Surface 

 smooth. 



The five basals form almost an equilateral triangle that is 

 not visible in a side view except at the angle below the small 

 radial. They are abruptly bent down into the columnar cavity. 

 The three plates in the angles are quadrilateral, the other two 

 are triangular. There is not much difference in the size of the 

 basals. The positions of the subradial and the five radials are 



