41 



The external appearance of the calyx of this species somewhat 

 resembles P. allophylus and P. brittis, but the differences are 

 sufficient to at once distinguish it, if attention is paid to the form 

 and to the articulating facets on the first radials. The differences 

 are so great that no descriptive comparisons will serve any one in 

 distinguishing them. But the vault, in this species, is wholly 

 different from either of the above mentioned species and from 

 that of any other known Platycrinus. If generic distinctions can 

 be founded upon the vault, then this species does not properly 

 belong to Platycrinus or to any other described genus. But, as 

 we have only a fragment of the vault, we would not be justified 

 in founding a genus upon it. We are convinced, that it properly 

 belongs to the family Platycrinidce and is nearer, in structure, 

 to Platycrinus than to any other described genus, and hence, 

 provisionally, refer it to that genus. 



Found by the veteran collector and learned geologist, R. A. 

 Blair, of Sedalia, Missouri, in the Choteau limestone of that 

 locality, and now in the collection of S. A. Miller. 



BARYCRINUS EXPANSUS, n. sp. 



Plate IV, Fig. 2, view of the calyx, azygous side below. 



Species very large, robust. Calyx more than twice as wide as 

 high; plates very thick, highly convex; sutures distinct, sunken 

 at the angles. Column large, pentagonal. 



Basal plates comparatively small, less than one-fourth as large 

 as the subradials, wider than high, and forming a very shallow, 

 pentagonal, saucer-shaped cup. Subradials four or five times as 

 large as the basals, a little wider than long, nearly equal in size, 

 four hexagonal and one, on the azygous side, which is very 

 broadly truncated for the azygous plate, heptagonal. First radials 

 larger than the subradials, about three times as wide as high, 

 nearly equal in size, remarkably thick, and truncated a little more 

 than half the width for the reception of the second radials. The 

 ambulacral notch very small, and facet for the second radials 

 nearly perpendicular or having an inclination of not more than 

 ten degrees. Azygous plate quadrangular, wider than high and a 

 little more than half as large as a subradial. 



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