54 



lontjing to tho basal disc, the first iutoi-radial rests between 

 the superior hiteral sides of the first primary radials. It is 

 not as large as the corresponding plate last described, jjentag- 

 onal and is followed by a single plate, in the second range, 

 that unites with thi'ee plates belonging to the vault. This is 

 the smallest of the interradial areas and has only two plates 

 in it. In the azygous area as usual in the Actmocrinidw, the 

 first plate enters one of the re-entering angles of the basal 

 disc, and is in line with the first primary radials. It is longer 

 than wide, hexagonal and followed by two smaller plates, in 

 the second range, three in the third, and four in the fourth, 

 which unite with the plates of tho vault in a zigzag line, with- 

 out any definite mark of separation. 



The vault is convex, having the radial areas highly and 

 narrowly elevated with abruptly descending, wide interradial 



. 1 ■ ■ ■ 



areas. It is covered with numerous, rather small, convex, 

 polygonal plates. It had a small, subcentral proboscis, which 

 is broken off in our specimen, at the summit of the vault 



Found in the Chouteau limestone, a^ Sedalia, Missouri, by 

 Mr. F. A. Sampson, and now in his collection. 



AMPHORACRINUS SEDALIENSIS, n. .Sp. 



Pldte V, Fig. 34, summit vieiv of a smtill sjtecimen; Fig. 35, 



azygous side of <i large specimen; Fig. 3(>, basal 

 .; view of same; Fig. 37, summit view of same. 



Species from medium to large size. Calyx somi-elliptical, or 

 bowl shaped, onc-foui-th wider than high, broadly round(>d be- 

 low. In t(!r radial areas depressed between the ai-ni bases where 

 they unite witli tlie plates of tho vault. Plates convex, sculp- 

 tured, more or less stellate. No radial ridges. Column round, 

 medium size, and facet for attachment only slightly concave. 



Basals shcn-t, and forming an hexagonal disc only about one- 

 half wider tlian the diameter of the column. First radials a 

 little wider than long, three hexagf)nal, two heptagonal. S<'C- 

 ond primary radials about two-thiids as larg(> as the first, 

 longer than wide, hexagonal. Third jnimary radials shoft, 

 much smaller than the second, pentagonal, axillary and sup- 

 port on each upper sloping side a single secondary radial. 



