484 THE CRINOIDEA” CAMERATA OF NORTH AMERICA. 
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vertical ridge, which extends above the arm regions, enclosing the anal 
opening, which is directed laterally. Interdistichal spaces deeply grooved, 
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and occupied by a single minute piece. Ventral disk low, slightly convex, 
pentangular in outline. The ambulacra are tegminal and raised above the 
general level of the disk ; the food grooves covered by two rows of compara- 
tively stout pieces with a large nodose plate above each bifurcation. Pos- 
terior oral proportionally large, extended into an elongate node; the four 
others barely convex. Column small; the axial canal minute. 
Horizon and Locality.— Hamilton group; Louisville, Ky., Clark Co., 
Ind., and Alpina, Mich. - | 
Types in the Knapp collection at New Providence, Ind. 
fvemarks. — From Hall’s descriptions it seems to us probable that his 
Hamilton group of the State of New York, are all or in part identical with 
this species. As neither one of them is figured, and the types in the State 
Museum of Albany are not accessible to us, we are unable to make the neces- 
Actinocrinus cauliculus, A. precursor, A. pocillum, and A. calypso, from the | 
sary comparison. In 1881 we erroneously placed this species under Gennco- 
crinus. A subsequent comparison with the types shows clearly that it has 
essentially the characteristics of Aorocrinus. | 
Plate VIII. Fig. 1. 
1878. Awnertin; Iconogr. Crin. Suec., p. 7. 
1885. W. and Sp. ; Revision Paleocr., Part IIT., p. 125. 
BARRANDEOCRINUS Aneetin. 
The calyx in perfect specimens is invisible, being completely enveloped 
by the arms and pinnules, which hang down over it; and the specimens, when 
calyx is composed of comparatively few plates, and resembles Dorycrinus in 
the form of the dorsal cup, from which it differs essentially in the structure 
of tegmen and arms. 
Basals three, large. Radials quite irregular in outline; the posterior 
all the arms are in place, have a superficial resemblance to a Blastoid.. The 
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ones pentangular, the anterior one hexagonal, and the remaining two hep- 
tagonal. Costals two, the axillary very small, subtriangular, its upper angle 
sharply pointed. Distichals apparently but one in the calyx. Arms ten, 
very heavy, biserial, folding outward and recumbent over the calyx, cover- 
ing the latter completely, and leaving of the arms only the pinnules exposed 
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