310 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
Horizon and Locality.— Upper Helderberg group; Falls of the Ohio, 
near Louisville, Ky. 
Zype in the Lyon collection at Jeffersonville, Ind. 
Ltemarks. — Actinocrinus multicornus Lyon is undoubtedly a mere varia- 
tion of this species. ‘The addition of small spinous extensions upon the first 
costals and first interbrachials is not a sufficient reason for specific distinction. 
DOLATOCRINUS Lyovy. 
1857. Lyon; Geol. Rep. Kentucky, Vol. IIL, p. 482. 
1877. S.A. Mitrer; Cat. Amer. Paleoz. Foss., p. 77. 
1881. W. and Sp.; Revision Paleocr., Part II., p. 124 (Proceed. Acad. Nat. Sci. Phila., p. 298). 
Syn. Cacabocrinus — Hatt; 1862, 15th Rep. N. Y. State Cab. Nat. Hist., p. 187. 
Calyx depressed. Dorsal cup flattened below, sometimes to the full 
height of the costals; the plates generally ornamented with radiating 
ridges and nodes. Ventral disk but slightly elevated, surmounted by a 
large, almost central tube; the interambulacral spaces depressed. Basals 
anchylosed, the lines of union obliterated. Radials large and hexagonal. 
Costals two; the first quadrangular, with convex upper and lower faces, 
narrower than either radials or second costals, and wider than long; the 
upper one pentangular, Distichals two to four in species with only two 
primary arms; but when there are additional bifurcations in the calyx there 
is but one. Ambulacral openings large, arranged in groups, with wide 
interspaces, and directed upwards. Arms biserial, generally bifurcating. 
Interbrachials rather numerous, there being generally three ranges. The two 
proximal rows consist of a single plate each, of which the first is the largest 
plate of the calyx, rising to the top of the first distichals; the upper row 
connecting insensibly with the interambulacral plates. The latter plates 
consist in most of the species of a single row of from five to seven rather 
large cuneate pieces — the smaller end directed downward — which, except 
the three middle ones, are not in contact laterally throughout their full 
length, their lower ends being slightly excavated, so as to leave narrow slit- 
like openings between the plates, two to three to each side of the interradius, 
or four to six to the whole area. Some species have two rows of interambu- 
lacral plates instead of one, four to six smaller ones being placed beneath the 
others, and the upper margins of these plates are slightly pierced by the 
lower ends of the slits. Above the interdistichal areas, there are rarely more 
than two slits, and not exceeding four. In the dorsal cup, the arrangement 
