BATOCEINID^. 403 



coistals ; followed by 2 X 4 palmars, except in the anterior ray, which has 

 three distichals and no palmars. Arm facets large, jjrojecting, directed out- 

 ward. Arm openings arranged in groups; the interspaces between the rays 

 twice as wide as the others, and slightly depressed. Arms eighteen ; their 

 structure is not known, but they were evidently large. Interradials one or 

 two, very small, and arched by the palmars. Anal plate shorter and nar- 

 rower than the radials ; it is followed by three and one plate of nearly equal 

 size, and by a narrow elongate piece at the arm regions. Ventral disk about 

 as high as the dorsal cup, hemispherical, slightly bulging along the sides, the 

 principal plates sharply nodose. Posterior oral strictly central, more spinous 

 and larger than the four others ; the radial dome plates arranged in groups 

 of three over each ray. Anal tube excentric and very small. 



Horizon and Locality. — Lower Burlington limestone, Burlington, Iowa. 



Types in the collection of Wachsmuth and Springer. 



Eretmocrinus coronatus (Hall). 

 Plate XXXVII. Figs. 7a, h, c. 



1S60. Actliioeriniis coronatus — Hail; Suppl. Geol. Eep. loiva, p. 28, Photogi'. Plate 4, Figs. 1 and 2 



(1.873, N. Y. State Bull. I.). 

 1873.. Eretnocriims coronatus — Meek and Worthen ; Geol. Rep. Illinois, Vol. V., Plate 10, Pigs. 



8(z, b, c. 

 1877. Actinocriims coronatus — S. A. Miller; Amer. Palffioz., Poss., p. 66. 

 1881. Eretmocrinus coronatus — W. and Sp. ; Revision Palseocv., Part II., p. 173. 

 1890. Eretmocrinus coronatus — S. A. Miller; North Amer. Geol. and Palseont., p. 282. 



A somewhat aberrant form, in its general habitus approaching Dori/crinus. 

 Calyx about as high as wide. Dorsal cup a little shorter than the ventral 

 disk, broadly truncate at the lower end, where its diameter is equal to one 

 half the width at the top ; a little lobed at the arm regions. The plates are 

 highly convex or nodose, the suture lines distinct. 



Basals stretched out horizontally, and sometimes hidden almost entirely 

 by the overhanging nodes of the radials; they are deeply notched at the 

 suture lines, forming a sort of trilobed plane, which in the central part is 

 slightly excavated for the reception of a very small column. Radials moder- 

 ately large, the two heptagonal ones with sharp salient angles, which fit in 

 and rest within the lobes of the basal disk, and form a part of the lower 

 surface. First costals quadrangular, twice as wide as long, narroAver than 

 the radials ; the upper and lower faces straight. Second costals pentangular, 

 generally a little longer than the first, and somewhat wider. Distichals two ; 



