fe ee ne _— . — —— = — - re $< a -- 
402 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
Interbrachials one and two, the first almost as large as the radials, the two 
upper ones either arched by the palmars, or followed by an additional elon- 
gate piece, which is interposed between the palmars and connects with the 
interainbulacral plates. Anal plate narrower and higher than the radials, 
ve = et 
~~ 
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succeeded by three large, somewhat elongate plates, which support two or * 
three smaller ones, and these another which rests between the arm bases. 
Ventral disk a little lower than the dorsal cup, irregularly hemispherical ; 
plates convex, the orals and radial dome plates of the tegmen larger and 
more protuberant than the intervening plates, the posterior oral nearly 
central and twice as large as the four others. The radial dome plates are 
placed near the periphery, there being three large pieces over each ray, one 
above each arm pair, except in the anterior ray, in which there is but one 
piece. Anal tube large, subcentral, composed of nodose plates, Structure 
of arms not known. | 
i florizon and Locality.— Lower Burlington limestone; Burlington, Iowa, : 
| and Sedalia, Mo. 
Type in the University Museum at Ann Arbor, 
_Eretmocrinus rugosus W. and Sp. (nov. spec.). 
Plate XXXVI. Figs. 9a, b, ¢. 
A small, well marked species of the type of Eretmocrinus leucosia. — Calyx 
wider than high, distinctly lobed at the arm regions, Dorsal cup depressed, 
broadly truncate at the base; the sides, which at their lower end spread 
but very little, expand abruptly from the top of the costals, and form a 
rim, which is almost at right angles to the base. Plates highly elevated: 
( | the radial ones formed into conspicuous rounded ridges, which extend to 
i the entire width of the plates; the interradial ones into rounded nodes. The 
surface of the ridges is covered by small, elongate prominences, forming 
longitudinal rows; the top of the interradial nodes by similar excrescences 
which have a radiating tendency. 
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a NN nna 5 
Basals extremely large, spreading outward and downward, and forming 
| a broad rim, of which the suture lines are deeply indented at the sides and 
| distinctly grooved at the lower face; the surface of the plates up to the 
column facet is covered by fine, rugose striz. Radials short, more than twice 
as wide as long. Costals narrower and shorter than the radials; the first 
quadrangular, the second pentangular. Distichals 2 X 2, smaller than the 
re a = 
