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. Regular 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. 
Remarks. — Prof. Hall made this species a variety of MZ. striatus. It is, 
however, sufficiently different to be recognized as a distinct species, which 
we believe is more nearly related to IZ. fasciatus than to MW. striatus. 
Macrostylocrinus Meeki (Lyon). 
Plate XXII. Figs. 16a, b. 
1861. <Actinocrinus Meeki — Lyon ; Proceed. Acad. Nat. Sci. Phila., p. 411, Plate 4, Figs. 4a, 0. 
1881. Macrostylocrinus Meeki — W. and Sr. ; Revision Paleocr., Part I1., 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 
obseure triangles. The inner spaces of these triangles are occupied by fine 
closely arranged striz, which form additional triangles one within the other ; 
there being five 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 coneave and forming an acute angle. First 
interbrachial large, a little longer than wide, resting against the distinctly 
sloping sides of the 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 strue- 
ture of the arms. 
