312 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 



the whole of the first costals^ spread out horizontallj^ ; while the second 

 costals and distichals turn straight upward. The ornamentation of the dorsal 

 cup consists of two or three rows of parallel ridges^ which pass out from the 

 middle of the plates — with or without interruption — to adjoining plates, 

 so as to form numerous concentric triangles. A more conspicuous ridge 

 passes up and down the rajs. Another, equally prominent, connects the 

 radials laterally, and forms a pentagon around the basal concavity. The 

 radials, first costals and first interbrachials are each surmounted by a promi- 

 nent node, while the plates of the tegmen are covered with small, granular 

 prominences. 



Basals small, almost completely concealed by the column ; forming a 

 conspicuous cone at the inner floor of the calyx. Radials larger than first 

 and second costals together, their greatest width equal to their length ; 

 their upper lateral faces shorter than the lower. First costals once and 

 a half as wide as long, the upper and lower faces somewhat convex. Second 

 costals a little longer and wilder than the first. Distichals 2 X 10 in the 

 calyx ; the low^er one almost as large as the preceding axillary ; the others 

 small, and supporting the arms of which there are two to the ray. Arm 

 bases projecting ; the ambulacral openings large. First interbrachials as 

 large as the radials and first costals together; they rise to the height of the 

 first distichals, and are followed 'by a single much smaller plate in the second 

 row, and three still smaller ones above, which support three or four plates 

 in the disk. Orals and radial dome plates well defined, larger than the inter- 

 ambulacrals. Anal tube almost central. Column round ; the axial canal 

 large and pentalobate. 



Horizon and Locality, — Hamilton group ; in the limestone bed above the 

 Black Slate ; Louisville, Ky. 



Ti/pe in the Lyon collection at JefFersonville, Ind. 



Dolatocrinus Marshi Lyon. 

 Plate XXVI. Figs, la, h, c, d. 



1869. Lyon ; Trans. Amer. PLilos. Soc, Vol. XHI., p. 461, Plate 37, Tigs, n, nl, n 2. 

 1881. W. and Sp.; Revision Palseocr., Part XL, p. 126. 



Calyx of medium size, wider than high. Dorsal cup basin-shaped, the 

 bottom deeply excavated and truncated to near the top of the second 

 costals; the sides gently curving upward to about a vertical position; the 



