204 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
ambulacral plate is somewhat wider, and perforated by the anus to such an 
extent as to leave only a narrow skeleton at the lateral margins. 
Gazacrinus Miller is identical with Jdiocrinus, the latter name having 
priority. Miller described the genus as monocyclic instead of dicyclic, and 
he speaks of a “ vault sustained by a specialized frame work with ambulacral 
canals connecting the arms with the central orifice.” This is misleading, for 
the plates exposed at the oral surface are true plates of the disk, and the 
open spaces which appear in the specimens were closed by orals and ambu- 
lacral plates. There was no central orifice, the peristome being covered as 
in all other Camerata. 
FTorizon and Locality. — Upper part of Niagara group; St. Paul, Shelby 
Co., Ind. 
Type in the collection of Wachsmuth and Springer. 
Remarks. — Mr. Miller, in describing the arm plates of this species, 
states they are long, and their edges “are transversely serrated on the 
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inside, half the depth of the plates.” We observed this structure in our 
specimen, and were at first inclined to regard the edges as formed of small 
side pieces, and so described them in the “ American Geologist.” Since then 
on further cleaning the specimen, we have become convinced that the parts 
in question are mere extensions of the arm plates, which are short, and that 
the line of union is slightly gaping to facilitate motion. 
Another point in Miller’s description should be noticed. He says: “There 
are three longitudinal furrows on the inside of each radial series, shown at 
the top of the secondary radials; this gives fifteen furrows at the top of the 
secondary radials, one in the middle of each plate, and the other at the 
suture ;”’ and he alludes to this as a peculiarity entirely new to him. He 
evidently misunderstood the structure, for our specimen clearly shows but 
one furrow to each brachial, of which those from the distichals unite upon 
the axillary costals at the extreme edge of the disk. The supposed marginal 
furrows do not enter the disk, and are mere depressions at the lateral margins 
of the distichals, formed by the highly projecting serrated edges of the 
ambulacral furrows at each side. 
