324 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 



Dolatocrinus tuberculatus W. and Sp. (nov. spec). 

 Plate XXV, Fig. 3. 



Of the type of D. ghjptus Hall^ but diflering in the style of ornamenta- 

 tion. Dorsal cup not twice as wide as high ; subglobose, slightly depressed 

 from the middle of the radials downward -, central concavity small, elliptical^ 

 formed by the basals only, and completely filled by the upper column joints. 

 The radials, costals and first interbrachials are each elevated into a large, 

 very conspicuous tubercle, and the tubercles are connected by well-marked 

 ridges. There are generally four parallel ridges from the interradial to the 

 radial nodes, and the same number between the radials and first costals, 

 which form ^\q sets of four triangles around the column at some distance 

 from it; those of the same set concentric. The costals are connected with 

 the first interbrachial by two ridges, while there is but one ridge, but more 

 prominent, between the distichals. Other ridges connect the distichals with 

 the higher interbrachials. Basal disk small, almost completely hidden by 

 the column, and surrounded by a prominent circular rim with small nodes 

 interradially disposed. Radials large, almost as long as wide, much larger 

 than the first costals ; the second costals higher and wider than the first. 

 Distichals apparently two, each one provided with a short node. First inter- 

 brachial smaller than usual in this genus ; followed by a quadrangular plate 

 in the second row, and three smaller plates above. Nothing is known of 

 ventral disk and arms. 



Horizon and Locality. — Hamilton group ; Clark Co., Ind. 



T(/pe in the collection of Mr. Victor W. Lyon. 



STEREOCRINUS Barris. 



1878. Barris; Proceed. Davenport Acad. Nat. Sciences, Vol. H., p. 283. 



1881. W. and Sp. ; Eevision Palseocr. Part II., p. 126 (Proceed. Acad. Nat. Sciences, Phila., p. 300). 



1885. Barkis; Proceed. Davenport Acad. Nat. Sciences, Yol. IV., p. 103. 



1889. S. A. Miller; North Amer. Geol. and Pal^ont., p. 283. 



In general form, ornamentation, and the arrangement of plates resem- 

 bling Dolatocrinus, but having one costal instead of two, and a tripartite 

 base. Dorsal cup depressed, truncate below. Basal disk small, pentagonal ; 

 composed of three pieces, of which the suture lines are generally visible. 

 Radials and costals nearly of equal size ; the former hexagonal, the latter 

 pentagonal and axillary. Distichals two or three, supporting the arms. 



