pe Se en —— 
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976 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
slightly projecting outward ; axial canal very small. Radials and anal plate 
nearly or fully as long as wide. First costals one third smaller than the 
radials; the second costals narrower than the first, and smaller generally. 
Higher brachials gradually decreasing in size upward, each one support- 
ing an arm at one side, and the upper one two arms. Arms normally oy 
eight to the ray; small, to judge from the size of their facets. Regular 
interbrachials: 1, 2, 2, against 2, 3, 2 at the anal side, followed by two 
very small pieces between the lobes. Interaxillaries one, which, like the 
interbrachials, meets with the plates of the tegmen. Ventral disk less than 
one third the height of the calyx, depressed conical, deeply grooved toward 
the margin. The plates are quite small, scale-like, slightly convex, and: of 
nearly uniform size. Orals indeterminable, but there are along the line of 
the ambulacra, over each ray, three plates somewhat larger than the others, 
which may represent radial dome plates of a first and second order. Anal 
tube almost central, small for the genus. 
Horizon and Locality. — Lower Burlington limestone ; Burlington, Iowa. | | 
Type in the Illinois State Collection at Springfield. 
Remarks. — This species, which represents a transition toward Teleio- 
erimus, is readily distinguished by the depressed form of the disk, and the 
scale-like plates of which it is composed. 
Actinocrinus trijugis (S. A. Mixer). 
Plate LIV. Figs. 4a, b. 
1891. Blairocrinus tryjugis—S8. A. Mittnr; Adv. Sheets 17th Rep. Geol. Surv. Indiana, p. 69, Plate 11, 
IRWESy Ee ig 
A small species of the type of A. tenwisculptus. Calyx wider than high, 
distinctly lobed between the arm bases. Dorsal cup low cup-shaped, about 
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twice as wide as high, the sides rapidly spreading and convex. Surface of | 
plates covered with angular radiating ridges, which meet in a small node at ; 
the centre of the plates; there being one ridge to each side except from the | 
antero-lateral radials and anal plate, whence two ridges pass to the basals. | 
The ridges passing up the radials and brachials somewhat the strongest. | 
Basals small, forming an almost flat hexagonal disk, which is but little 
larger than the column, and has a small, pentangular axial canal. Radials 
large, nearly as long as wide. First costals quadrangular, twice as wide as 
long; the second a little larger and pentangular. Distichals moderately 
3 
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