590 THE CRINOIDEA CABIERATA OF NORTH AMERICA. 



Horizon and Locality. — Lower Burlington limestone ; Burlington, Iowa, 

 and Lake Valley, New Mexico. 



Type in the (Worthen) Illinois State collection, Springfield. 



Remarks. — With the excellent material before us, we have attempted in 

 vain to separate from this species Actinocrinus jolanoladlis Hall, Aciinocriims 

 quadrispinus White, and Amphoracrinus divergens, var. midtiramosus M. and W. 

 We admit that in some of the specimens the radials and costals are com- 

 paratively shorter, the number and branching of the arms slightly different, 

 and the surface ornamentation somewhat coarser or almost obsolete ; but 

 these characters appear to be independent of each other. Nor can the fork- 

 ing of the oral spines, upon which ISIeeli and Worthen proposed a variety, be 

 considered a valid distinction, because it occurs as well in the smaller speci- 

 mens of the type of A. quadrispbms, as in the typical form of Amphoracrinus 

 divergens. 



Amphoracrinus viminalis (Hall). 

 Plate LIV. Fig. 8. 



18G3. Actittocrinus viminalis — Hall; 17tli Rep. N. Y. State Cab. Nat. Hist., p. 54, and 1S75, Geol. Surv. 



Ohio, Palfeont, Vol. II., p. 165, Plate IT., Fip;s. 12 to 14. 

 1881. AmpJioracrimis mminalis — W. aad Sp. ; Eevisiou Palffiocr., Part II., p. 155. 



Below medium size. In the form of the dorsal cup, stj'le of ornamenta- 

 tion, as well as the general structure and mode of branching of the arms, 

 resembling the preceding species. Dorsal cup dejjressed turbinate, the sides 

 rapidly and uniformly spreading from the truncated base to the top of the 

 costals, above which the brachials form free lobes, which droop to aljout the 

 first bifurcation of the arms, leaving only the basals and radials visible from 

 a side view. Plates almost flat, except for the general curvature, but owing 

 to the rather deep grooves at the sutures they have the appearance of being 

 slightly convex ; their surface obscurely granulated. 



Basals forming a very short, subhexangular cup, which slightly projects 

 over the sides of the column ; the interbasal sutures distinct but not grooved. 

 Eadials two thirds as long as wide, and as large as, or larger than, both cos- 

 tals together ; the lower sloping sides much longer than the cori-esponding 

 upper ones. First costals quadrangular, three times as wide as long ; the 

 second smaller than the first, broadly triangular in outline ; they are followed 

 by 2 X 2 short, quadrangular distichals, which are connected laterally by 



