408 THE CEINOIDEA CAMERATA OF NORTH AMERICA. 



supports 2X2 fixed palmars, and these the arms. The arm-bearing plates 

 are once and a half as wide as those below or above, and in contact laterally. 

 Their facets are irregularly crescent-shaped, and directed shghtly upward ; 

 they do not occupy the middle of the plates, but lean to the inner sides of 

 the rays, and leave large interspaces between adjoining rays. By means 

 of this structure the arms are formed into groups as effectually as in other 

 species by the interposition of interbrachial plates. The arms, which have 

 not been observed in this species, were evidently quite ponderous to judge 

 from the large size of their facets, and composed of two rows of short, leaf- 

 like pieces, similar to those oi Agaricocrinus. Interbrachials one; the plate 

 large, higher than wide, and arched by the arm-bearing brachials. First 

 anal plate followed by a very long second, which rises to above the level of 

 the arm bases, and rests between two short interbrachial pieces. Ventral 

 disk more than three times as high as the dorsal cup ; the plates large and 

 of about uniform size; the anal tube occupying the central part. The 

 posterior oral is the largest plate of the tegmen, and, like the other orals, is 

 pushed over to the anterior side. The ambulacra are subtegminal, their 

 upper portions being covered with superimposed interambulacral pieces, but 

 on approaching the arms by large radial plates of a first and second order. 

 The respiratory pores are large, and jilaced at some distance from the ambu- 

 lacral openings. 



Horizon and Localiti/. — Keokuk group; Pilot Knob, near Louisville, Kj'.; 

 White's creek, near Nashville, Tenn., and New Ross, Montgomery Co., Ind. 



Bemarks. — Miller's Alloprosallocrinus Ckirleyi is a small example of 

 A. conicus, in which one of the posterior rays has but two arms. 



EUTROCHOCRINUS W. and Sp. (nov. gen.). 



. (E5 well, Tpoxo9 a wheel, KpCvov a lily). 



Calyx large, wheel-shaped, narrow to the top of the radials, thence 

 spreading abruptly until the sides of the dorsal cup are at right angles 

 to the axis of the calyx. Ventral disk almost flat to near the base of the 

 anal tube. Basal cup deep, subcylindrical, composed of three equal plates. 

 Radials larger than both costals together; the first costal transversely linear, 

 the second depressed pentangular. Distichals and palmars increasing in 

 width upward. Ambulacral or arm openings equidistant or nearly so ; 

 directed sidewise. Arms single or in pairs, biserial, rounded, very short and 



ii 



