THYSANOCRINID®. 195 
sides of the ridge, small radiating lines pass out to the interbrachials, form- 
ing triangles of which the intervening spaces are granular or covered with 
fine striations. Stronger ridges pass from the radials to adjoining basals, 
where two of them meet, and proceed asa single ridge to the infrabasals. 
The latter ridges form around the column a sharply defined pentagon, whose 
salient angles lie in a radial direction. 
Infrabasals of moderate size, forming a narrow belt around the column, 
which is visible in a side view. Basals large, without nodes, rapidly spread- 
ing. Radials larger than the costals, second costals narrower than the first. 
Arms apparently ten, of which in mature specimens the six or seven lower 
plates are incorporated; arm plates comparatively large, elongate, and 
slightly wedge-form. Interbrachial plates large; arranged: 1, 2, 3, 3, with 
a fifth row at the level of the arm bases. Anal interradius considerably 
wider, having three plates in the second row, and four in the third ; — there 
being no continuous row of anal plates or any sort of elevation. Interdis- 
tichals five to seven. Ventral disk unknown. Column round; axial canal of 
moderate size; pentalobate, the lobes directed radially. 
Horizon and Locality. — Niagara group; Waldron and Hartsville, ind. 
Types in the American Museum Natural History, New York. 
Remarks. —This species differs from Thysanocrinus inornatus in the larger 
size of the infrabasals, the arrangement of the plates of the anal side, the 
absence of an anal ridge, and in the general ornamentation of the plates. 
Glyptaster occidentalis (var.) inerebescens is, in our opinion, not sufficiently 
distinct to be ranked as a variety. 
Thysanocrinus brachiatus Hatt. 
Plate XVIII. Fig. 7. 
1852. Glyptaster brachiatus — Haut ; Paleont. N. York, Vol. IT., p. 187, Plate 41, Vig. 4. 
1881. Glyptaster brachiatus — W. and Sr.; Revision Palwoer., Part II., p. 196 (Proceed. Acad. Nat. Sci., 
Phila., p. 370). 
Calyx subglobose, having very strong radial ridges which bifureate at 
both ends. The lower branches proceed to the basals, and produce a well 
defined pentagon, subdivided into five nearly equal fields by another row of 
ridges; the upper branches follow the distichals, and pass into the arms. 
The general surface without ornamentation. 
Infrabasals small, but exposed beyond the column, and visible even in 
a side view. Basals of moderate size. Radials deeply notched for the 
