440 THE CRINOIDEA CAMEEATA OF NOETH AMERICA. 



Lobocrinus sequibrachiatus (McChbsnet). 

 Plate XXIX. Figs. 8a, l, and Plate XLVI. Figs. 6a, I. 



I860. Actinocrinus aiuibrachiatus — McChesmet; New Palffioz, Foss., p. 25. 



1S67. Actinocrinus eequibracUattis — McChesney; Traus. Cliic. Acad. Sci., p. IS, Plate 4, Tigs. 2 aud 5. 



1873. Batocrinm aqidbrachiatus — Meek and Worthen ; Geol. Rep. Illinois, Vol. V., p. 368. 



1881. Batocrimis aqaibrachiatus — VY. aud Sp. ; Revisiou Palajocr., Part II., p. 165. 



Intermediate between Eutrochocriims Lovei and Lobocrinus pyriformis ; 

 differing from the former in the much broader base, and in having the 

 arm bases directed iijjwards and arranged in groups ; from L. jiyriformis 

 in the less elongate calyx, in the depressed form of the ventral disk, the 

 comparatively longer arms, and in the shorter and more slender anal tube ; 

 and from both in being decidedly lobed between the rays. Calyx as high as 

 wide ; the dorsal cup one third higher than the ventral disk, broadly trun- 

 cated at the base, the sides concave, gradually widening to the top of the 

 first costals, thence rapidly spreading to the arm facets, which are directed 

 upward. Plates of the dorsal cup perfectly flat and smooth, those of the 

 ventral disk more or less convex. 



Basals forming a nearly cylindrical cup, more than twice as wide as high ; 

 interbasal sutures indistinct. Radials nearly as long as wide, the upper end 

 a little wider. First costals quadrangular, once and a half as wide as long ; 

 the second fully twice as wide as long, heptangular ; their upper angles 

 obtuse. Distichals 2X2, the second axillary and larger than the other 

 brachials ; followed by a single row of palmars, which support the arms. 

 Arm openings arranged in groups of two, the interspaces larger between the 

 main rays than between their subdivisions. Arms twenty, of moderate size 

 and length, frequently infolding at the top, which makes them appear 

 shorter than they really are. Interbrachials from five to nine, generally 

 continuous with the interambulacral plates at all sides, but always at the pos- 

 terior side. Anal interradius composed of ten to fourteen pieces ; the anal 

 plate higher than the radials ; followed by three ranges of three plates each, 

 and a few narrow pieces interposed between the arm bases. Ventral disk 

 depressed conical, the plates rather large and of almost equal size. Anal 

 tube nearly central, composed of tumid plates. 



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

 Burlington, Iowa. 



