Description of New Genera of Echinodermata. 17 
HYDREIONOCRINUS PENTAGONUS, n.sp. ~~ 
Plate I1., Fig. 6, view of azygous side showing hight of calyx and 
upper truncated face for second radials; Fig. 7, basal view. 
Calyx large, pentagonal and exceedingly depressed to the top of 
the first radials ; plates very thick and sutures well defined; basals 
rather large and forming an octagonal ring around the end of the 
column, against the faces of which the subradials and three of the 
radials rest ; subradials small, three triangular, one quadrangular, 
and the other pentagonal by reason of supporting the first azygous 
plate; they are slightly convex, and le in furrows made by the - 
angular convexity made by the first radials; first radials about twice 
as wide as high, the hight not much exceeding the thickness of the 
plates; the plates are hexagonal, highly convex, depressed toward 
the sutures, and truncated upon the outer faces, so as to give the 
calyx a pentagonal outline ; the depressions at the sutures appear 
as furrows in the pentagonal outline of the calyx; first azygous 
plate quadrangular, narrow, resting upon the upper sloping side of 
a subradial and forming the bottom of the furrow between two first 
radials; second azygous plate heptagonal, slightly truncating two 
first radials ; column round. 
Second radials and succeeding parts above unknown, and it is 
therefore possible that this species is a Zeacrinus, but from the char- 
acters given the inference is, it possessed the ventral sac of an 
Hydreionocrinus, beside the latter genus had, so far as known, its 
greater development in the Upper Coal Measures, while the former 
is more characteristic of the upper part of the Subcarboniferous 
or Kaskaskia Group. It is unnecessary to compare this with any 
species heretofore defined, because it is easily recognized by its 
strongly marked characters. 
Collected inthe Upper Coal Measures at Kansas City, and now 
in the cabinet of Wm. F. E. Gurley, of Danville, Illinois. 
ONYCHOCRINUS ULRICHI, n. sp. -~ 
Plate I11., Fig. 2, azygous side; Fig. 3, symmetrical side, natural size. 
Calyx depressed, saucer-shaped; plates finely granulous, sutures: 
distinct; basals three, extending slightly beyond the column; four 
of the subradials pentagonal, the one opposite the azygous side 
