51 



the left of the azygoiis area, if normal, will distinguish this 

 species from all others and as the ray on the right is the 

 same in each spt^cimen we think the one on the left is normal. 

 The general form and surface ornamentation will distinguish 

 this from all other species having twenty arm openings to the 

 vault, though it resembles A. fossatus which has forty arm 

 openings to the vault. 



Found by R. A. Blair, in the Burlington Group, at Sedalia, 

 Missouri, and now in the collection of S. A. Millei-. 



SAMPSONO(,"RiNus, n. gen. 



[Ety. The cjeneric name is inlended as a compliment to a (Us- 

 IvKjiii^hid naluralisi, Mr. F. A. Sampson, of Sedalia, Mo.\ 



Body more or less globose. Basals three, subequal, one 

 pentagonal, two hexagonal. Primary radials either two or 

 thiee in each radial series and differing in this respect 

 in the different radial series in the same specimen. 

 Secondary and tertiary radials present. Interradial plates con- 

 nect with those of the vault, and, in three of the areas the 

 first plate abuts upon the basals, by which arrangement eight 

 plates unite with the basal disc. Vault elevated over the 

 ambulacral canals, and depressed in the interradial s]iaces. 

 Probo.scis subcentral. Type S. hemisphericus. 



We refer this peculiar genus to the family Actinocrinidyo. 



SAMPSONOCUINXTS HEMTSPIIEUICUS, n. .sp. 



Plate III, Fig. 7, basal rnew; Fig. S, summit view; Fig. 9, 



azugous side, the sutures tyetween some of the plates 



being obscure; Fig. 10, lateral vietr. 



General form of the calyx heniisi)herical, rather more than 

 one half wider than high, broadly rounded below. Plates 

 convex. Surface granular. Columnar facet very small. Ai-ms 

 directed horizontally. 



One of the basal plates is pentagonal and two hexagonal, 

 and they differ but little in size. When united tliey form a 

 disc having three re-entering angles, in one of whicli an azygous 

 plate is su])])oi-ted, and each of the others suppoi-t. a radial series. 

 The jientni'onal plate is truncated by a radial and the hexagonal 

 plates aie truncated by a radial and by an interradial. By 



