41 



The external appearance of the calyx ol' this si)eeies somewhat 

 resembles P. dllophyhis and /'. Iiriliist, hut the difl'ereuces are 

 sufMcient to at once distinyuish it, if atteuti<3n is paid to the form 

 and to the articulatinjj; facets on the first radials. The differences 

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

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

 (lifF(M'ent from either of the above mentioned species and from 

 that of any other known I'lati/eriiiios. If generic distinctions can 

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

 belong to r/ntycriniis 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 I'hil ijrriniilif and is nearer, in structure, 

 to Platycfinus 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. 



BARVt'RIXUa EXPANSUS, n. Sp. 



I'liitc / I '. /'Vi.''. ..'. rii'ii- of the cali/.v, ri-.i/goiix side beloir. 



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 oi' 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. 



— G 



