406 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 



divisions, which is followed by 2 X 2 palmars and two arms ; but in the 

 anterior divisions by 2 successive distichals and a single arm. The anterior 

 ray, which has but one arm in both divisions, has 2X2 distichals. Arm 

 facets subcircular, concave, very large, and the surface covered with radiating 

 strias. Ambulacral openings quite small. Interbrachials : 1, 2, 1, 2 at the 

 regular sides, and 3, 3, 2, 2 on the anal side ; the upper row on a level with 

 the arm bases. Ventral disk inflated, considerably higher than the dorsal 

 cup, the conical upper end passing gradually into the anal tube. The plates 

 of tlie tegmen decrease slightly in size toward the periphery, and are covered 

 with sharp nodes as large as those of the dorsal cup. Orals excentric ; the 

 posterior one quite large. Anal tube stout and composed of large plates 

 with sharp elongate nodes; it is almost central at the base, but curves a little 

 to one side. Structure of arms and column unknown. 



Horizon and Locality. — Keokuk group ; White's creek Springs, near 

 Nashville, Tenn., Pilot Knob, near Louisville, Ky. ; Barren Co., Ky., and New 

 Ros.s, Montgomery Co., Ind. 



ALLOPROSALLOCRINUS Cass, and Lton. 



1860. Casseday and Lton; Proceed. Amer. Acad. Arts and Sci., p. 29. 



1866. Shdmaec; Catal. Palseoz. Poss. North Amer., Part I., p. 353. 



1873. Meek and Woethen (in part) ; Geol. Rep, Illinois, Vol. V., p. 368 (not M. and W., 1865, Proceed. 



Acad. Nat. Sci. Pliila., p. 164). 

 1879. Zittel; Handb. der Palseontologie, Vol. I., p. 370. 



1881. W. and Sp. ; Revision Palaiocr., Part II., p. 113 (Proceed. Acad. Nat. Sci. PUla., p. 287). 

 1890. S. A. Miller; North Amer. Geol. and Pateout., p. 222. 



Syn. Comcritms Thoost; List of Grin, of Tenn. (not defined). 



Calyx conical, almost flat below the arm bases. Basals three, equal. 

 Costals two, but generally so closely anchylo.sed that the line of union is 

 invisible, and there is virtually but one plate. Distichals one or more, 

 either followed by palmars, or directly supporting the arms. The arm-bear- 

 ing plates in contact laterally, except upon the anal side, where they are 

 separated by the second anal. Arms few to the ray, arranged in groups ; 

 their facets very large, subcircular and deeply notched at the upper end for 

 the reception of the ambulacra. The interbrachials, so far as observed, 

 consist of one large plate, except at the anal side, where the first anal is 

 followed by a second, which at each side has two short interbrachial pieces. 

 Ventral disk conical, its upper end gradually passing into the anal tube, 

 which is stout and almost central. The ambulacra subtegminal, their main 

 trunks covered by superimposed interambulacral pieces, which are followed 



