316 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
by broad, keel-like processes, which form into a knot in the centre of the 
radials and second costals. Another prominent ridge runs from the lower 
margins of the first interbrachials to the middle of the plates, where it forms 
a rather sharp node, from which two branches proceed to the upper lateral 
“ margins. The smaller ridges, of which there are three to four to each side, 
are marginal, extending but a short distance into the plates. 
Basals small, perfectly anchylosed, surrounded by a circular ridge, and 
entirely covered by the column. Radials larger than the costals, hexagonal, 
wider than long, widest above the middle and not visible from a side view. 
First costals short, quadrangular; the second considerably wider, a little 
longer and axillary, giving off to one side an axillary distichal, which sup- 
ports a small palmar at each side, and this an arm. The opposite distichal 
gives off a single arm from the second plate, thus making three primary arms 
to the ray. Arm bases projecting, giving to the calyx, as seen from above, 
a pentagonal outline. Structure of the arms unknown. Interbrachials: 1, 1, 
3; the first large; the second much wider than high; the middle plate of the 
third row comparatively large; the two at the sides as long, but narrower. 
Ventral disk composed of but few large plates, which are covered with several 
minute pustules of irregular arrangement; the interambulacral spaces 
depressed, consisting generally of only two plates, which abut against the 
orals. There are no interdistichals. Orals and ambulacral plates arranged 
as in the preceding species. Anus subcentral. 
Florizon and Locality. — Hamilton group; near Thedford, Ontario. 
Type in the Canada Survey Museum at Ottawa. 
Remarks. —1t is barely possible that Hall’s Cacabocrinus Troosti, from 
Western New York, is identical with this species, but it is described with 
four primary arms instead of three. 
Dolatocrinus triadactylus Barris. 
Plate XX VI. Figs 4a-d. 
1884. Barris; Proceed. Davenp. Acad. Nat. Sciences, Vol. IV., Plate 2, figs. 
1885. W. and Sp.; Revision Paleocr., Part III., p. 105. 
77 
a 
| 
Of medium size. Calyx depressed, a little wider than high. Dorsal cup 
broadly basin-shaped; the lower portions truncate to near the top of the 
first costals, then curving rapidly upwards, a little constricted below the arm 
bases; the basals moderately excavated, and the margin of the cavity 
