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 

 interambnlacral plates. Anal plate narrower and higher than the radials, 

 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. 



Horizon and Localiiy. — Lower Burlington limestone; Burlington, Iowa, 

 and Sedalia, Mo. 



Type in the University Museum at Ann Arbor. 



Eretmocrinus rugosus W. and Sp. (uov. spec). 

 riate XXXVI. Figs. 9a, h, c. 



A small, well marked species of the tj'pe of Eretmocrinus Imcosia. 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 

 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. 



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 striae. Radials short, more than twice 

 as wide as long. Costals narrower and shorter than the radials ; the first 

 quadrangular, the second pentangular. Distichals 2X2, smaller than the 



