290 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 



first, their upper angles acute. Arms two to the ray, free above the first 

 plate, which is longer than wide. The arms, according to Hall, are long, 

 slender, and simple. Kegular interbrachials slightly convex; arranged: 1, 

 2, 3. Anal interradius much wider, composed of three plates in the first 

 range ; the middle or anal plate longer than the two at the sides and fol- 

 lowed by a second anal piece, of which the top is on a level with the top of 

 the interbrachials of the third range. Structure of ventral disk unknown. 



Horizon and Locality. — Same as last. 



Eemarks, — Prof. Hall made this species a variety of if. striatus. It is, 

 however, sufficiently different to be recognized as a distinct species, which 

 we beheve is more nearly related to M.fasciatus than to M. striatus. 



Macrostylocrinus Meeki (Lyon). 

 Plate XXII. Figs. 16a, h. 



1861. Actinocrinus Meeki ~1jY0^ ; Proceed. Acad. Nat. Sci. Phila., p. 411, Plate 4, Pigs. 4^, b. 

 1881. Macrostylocrinus Meeki — ^. and Sp. ; Revision Palseocr., Part IL, p. 103. 



Calyx subglobose, about as wide as high ; cross-section slightly pentangu- 

 lar. A well defined ridge rises from the column, follows the median line of 

 the various radial plates, and passes into the arms. The ridge, which is 

 rather obscure upon the basals, gradually increases in size, and grows quite 

 prominent upon the costals. Smaller ridges proceed from the centre of the 

 radials to the interbrachials, and form with the larger ridges numerous 

 obscure triangles. The inner spaces of these triangles are occupied by fine 

 closely arranged striae, which form additional triangles one within the other ; 

 there being ^^q such sets of triangles around the column, which extend to 

 the middle of the radials, and are larger and better defined than any of the 

 others. 



Basals forming a shallow basin, rounded at the bottom ; the column facet 

 slightly concave. Radials fully four times as large as the first costals, and as 

 long as wide. First costal narrower than the second, and fully twice as wide 

 as long; the second somewhat larger, its sides spreading rather abruptly 

 upwards, the sloping upper faces concave and forming an acute angle. First 

 interbrachial large, a little longer than wide, resting against the distinctly 

 sloping sides of tlie radials, and rising to the top of the second costals ; the 

 succeeding plates much smaller. The arrangement of plates at the anal side 

 is not known ; neither is the construction of the ventral disk nor the struc- 

 ture of the arms. 



