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486 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
We have not seen the type specimens, and neither Miller’s figures nor his 
description enable us to make a satisfactory comparison. If it should prove 
to be the type of a new genus, the proposed name Cylicocrinus cannot be 
used for that form, as it was preoccupied in 1855 by Joh. Miiller for a 
Devonian genus. Miiller made the name “ Culicocrinus,’ which has the same 
derivation as Cylicocrinus. 
AGARICOCRINUS (Troost) Haut. 
1850. Troost; List. Crin. Tenn. (Proceed. Amer. Ass. Adv. Sci.), p. 60. 
1858. Haru (Subgenus of Actinocrinus); Geol. Rep. Lowa, Vol. I., Part II., p. 560. 
1861. Hawn (Subgenus of Amphoracrinus); Boston Journ. Nat. Hist., Vol. VIL. p. 280. 
1866. Munrx and WortHen (Subgenus of Actinocrinus) ; Geol. Rep. Illinois, Vol. II., p. 210. 
1873. Merrx and WorrueEn (Subgenus of Amphoracrinus) ; ibid., Vol. V., p. 499. 
1879. Zrvren (Subgenus of Amphoracrinus); Handb. der Paleont., Vol. I., p. 371. 
1831. W. and Sp.; Revision Paleocr., Part II., p. 109 (Proceed. Acad. Nat. Sci. Phila., p. 283). 
Calyx conical or depressed globose; the lower face concave, flat or 
broadly convex. SBasals three, small, arranged horizontally, and forming 
a hexagon, which is partly covered by the column. Radials rather small. 
First costals quadrangular, rarely hexangular; the second pentangular or 
hexangular according to the height of the interbrachials. Size of the second 
costals and first distichals extremely variable, sometimes the former being the 
largest plates of the calyx, and sometimes the latter. Arms two to four to the 
ray; the arm facets of the same ray contiguous, but each arm having a sep- 
arate ambulacral opening; the arm bases of adjoining rays separated by 
interbrachials. The earlier species have two arms to the ray, but most of the 
later ones three—some of them four —in the posterior rays, and two in the 
others. When there are but two arms, the first distichals are followed by 
a moderately short, somewhat cuneate second plate, which bends inward 
like an arm plate, and this again by two rows of short, heavy arm plates, of 
which the proximal one, and frequently those of the two succeeding rows, 
are in contact with their fellows of adjoining arms. The arm plates inter- 
lock with those of the opposite row, and the inner ones with the proximal 
distichals, which are also alternately arranged among themselves. Arms 
long and ponderous, heaviest at their bases, whence they taper gradually to 
the tips. Interbrachials three or more; in size as variable as the costals and 
distichals, but all of them narrow and long. In some species the first plate 
rises almost to a level with the arm bases, in others only to the middle of 
the first costals, and in this case the two plates of the second range are 
