BATOCRINID^. 399 



both sides of the arm is ornamented with a small spine, and these spines, 

 which are placed along the sides of the arms, increase in length and thick, 

 ness upward. Interbrachials three ; the first very large and spinous,- the 

 two upper ones merely convex. Anal plate higher than the radials, and 

 covered with a short central spine ; the three succeeding plates are simply 

 nodose, while the three or four small pieces above are scarcely convex. 

 Ventral disk shorter than the dorsal cup, depressed hemispherical ; the orals 

 and radial dome plates spiniferous ; the interambulacral plates nodose. Pos- 

 terior oral very large and central ; anal tube excentric and quite slender. 



Column large, the plates short. The older joints are twice as wide as the 

 intervening ones; the younger joints extremely short and flat at their sides. 

 At 4 cm. from the calyx there are in one of our specimens seven joints to 

 the internode, and these occupy only 4 mm. in leno-th. 



Horizon and LocalUi/. — Lower part of the Upper Burlington limestone, 

 Burlington, Iowa. 



Type in the White collection in the University Museum at Ann Arbor. 



Eretmocrinus corbulis (Hah). 

 Plate XXXVI. Figs. 5a, h, c, and 6. 



1861. AcUnocnnus corhdis — 'S.kli. ; Prelim. Descr. of New Crinoids, p. 1, and Boston Journal of Nat 



Hist., Vol. VII., p. 265. 

 1873. Batocrimis {Eretmocrinus) corbulis — Meek and Woethen; Geol. Rep. Illinois, Vol. T., p. 368. 

 1881. Eretmocrinus corbulis — W. and Sp. ; Revision Palaeocr., Part II., p. 173. 



Calyx subglobose, wider than high; the dorsal cup from one third to one 

 half higher than the ventral disk, broadly truncate at the lower margin, the 

 width at the base equal to one half the diameter at the arm bases, the sides 

 gently spreading and slightly convex. Plates nodose ; the nodes upon the 

 radials and brachials transversely arranged, those upon the interbrachial 

 plates subcircular; the surface smooth or obscurely granulated. 



Base short, the upper margin deeply notched along the sutures ; expand- 

 ing outward and downward, projecting conspicuously beyond the top of the 

 column, overhanging it, and forming a broad, shallow inverted basin. In 

 some specimens the basals are so deeply notched that the lower angles of the 

 radials, and that of the anal plate, constitute a part of the projecting rim, 

 and sometimes even enter the lower concavity. Eadials short, nearly twice 

 as wide as long, their nodes directed downward. First costals not more than 

 half the width of the radials, short, quadrangular, twice as wide as long, their 



