806 THE CRINOIDEA CAMEEATA OF NORTH AMERICA. 



rally occupies a radial position; but it does not agree with A. Shumardi. In 

 this species there are only two plates in radial succession ; the plate which 

 we described as the " second" radial rests upon two contiguous plates, which 

 are both interradial. 



The accessory pieces were multiplied by the addition of new rings above 

 the basals. This is well shown by the small specimen of A. Woriheni, and 

 by some of the smaller specimens of A. amjihora, in which the plates of the 

 last ring are yet trigonal, while in the larger specimens, with additional 

 rings, they are heptagonal. 



Acrocrinus Shumardi Yandell. 

 Plate LXXX. Figs. 1, 2, 3. 



1S47. Yandell and Shumakd; Coutributions Geology Kentucky, Plate 1, Tig. 3 Cfigured Tvithout descrip- 



tiou or name). 

 1855. Yandell; Amer. Journ. Sci. and Arts, Vol. XX. (new ser.), p. 135 (with figure). 

 1885. "W. and Sp. ; Revision Palseocr., Part III., p. 122. 



Syn. Acrocriims urnaformis — Hall; 185S, Gcol. Rep. Iowa, Vol. I., Part 11., p. 690, Plate 25, 



Figs. 9a, b. 



A large species. Calyx urn-fshaped, apparently more than twice as long 

 as wide ; the plates thin, almost flat, and without ornamentation. 



Basals forming a large basin ; the lower face rather broadly' truncated, 

 and extended outward into a small rim ; the interbasal suture slightly 

 grooved. The plates separating the basals from the radials arranged in 

 fourteen to twenty ring.s, more or less, each ring containmg from twenty-five 

 to thirty plates, except the upper one which has but eighteen. They are 

 arranged in a similar manner as in A. Woriheni, gradually increasing in size 

 upward, and the lower ones longer than wide, the upper as wide as long. 

 Eadials irregularly heptagonal, larger than any of the preceding plates, short 

 but extremely wide, their width being three to four times their height ; the 

 upper face of the radials is excavated to fully three fourths its width, form- 

 ing a deep, rounded facet, which encloses the costals and both distichals. 

 Anal plate a little longer than the radials, and like these supported by four 

 plates. Costals one, minute, trigonal, occupying about one tenth the width 

 of the facet. Distichals and palmars two, transversely linear ; the latter but 

 half the width of the distichals. Arms apparently eight to the ray, erect and 

 biserial. The structure of the disk has not been observed, but it was doubt- 

 less flat, and the anal opening, as shown by the specimens, frequently was 

 covered by a Gasteropod. Column of moderate size, composed of rather 



