608 THE CRINOIDEA CAMERATA OF KOETH AMERICA. 



IDacked, the joints longer, the spines more slender, and directed more nearly 

 outward. Interbrachials in three rows ; at the regular sides 1, 2, 1 ; at the 

 anal side 2, 3, 2, sometimes with a small plate wedged in between the pal- 

 mars, but generally the palmars are in contact laterally all around. Inter- 

 distichals 1 or 2, longitudinally arranged. Ventral disk high, convex ; the 

 orals and radial dome plates, which are represented by plates of a first, 

 second, and third order, large and spinous ; the interambulacrals not very 

 numerous, smaller and convex. Anal tube central, large and long, extend- 

 ing beyond the tips of the arms, and composed of irregular scale-like plates. 

 Column of medium side ; axial canal rather small. 



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



Ty2)e in the University Museum at Ann Arbor. 



EemarJcs. — In a very young specimen, evidently of this species, the 

 brachials are free from above the distichals ; the palmars and post-palmars 

 are more elongate in proportion, and uniserial and cuneate to the third plate, 

 resembling in their outlines the arm plates of certain PoteriocrinidEe. The 

 biserial plates above are also proportionally larger than in the older speci- 

 mens, but have already the characteristic ornamentation of this species. 



Cactocrinus limabrachiatus (Hall). 

 Plate LVIII. Figs. 9 and 10a, b. 



1861. Actinocrimts limabrachiatus — Hall; Descr. New Spec. Pal. Crin., p. 2; also Boston Journ. Nat. 

 Hist., Vol. VII., p. 268. 

 ISSl. Aclinoerinus liniabraehialus — W. and Sr.; Revision Palseocr,, Part 11., p. Ii4. 



Calyx bell-shaped, one third higher than wide, the arm bases slightly 

 projecting ; the dorsal cup fully once and a half as high as the ventral disk. 

 Surfiice of plates traversed by single series of angular ridges, continued from 

 plate to plate, and meeting at the centres, where they form sharp nodes. 

 Only the basals and radials are connected with one another by four or five 

 parallel ridges. 



Basals rather large for the genus, forming a spreading cup ; the suture 

 lines not grooved. Eadials a little longer than wide, their sloping upper 

 faces small. First costals short, quadrangular, rarely pentangular, the 

 upper and lower margins convex ; the second a little larger. Distichals 

 and palmars smaller in proportion. Arms six to the ray, given off as in the 

 preceding species, distinctly flattened on the back, the thi-ee or four proxi- 

 mal j)lates long and cuneate. Higher up, where the arms become biserial, 



