CRINOIDS. 165 



Megiatocrinus plenus White, 1802: Proc. Boston Soc. Nat. Hist., vol. tX, 



p. 16. 

 Megistocrinus parvirosiris Meek iSc Worthen, 1869 : Proc. Acad. Nat. Sci., 



Phila., p. 165. 

 Megisiocrinus parvirosiris Meek & Worthen, 1873: Geol. Sur. Illinois, vol. 



V, p. 399, pi. vi, tig. 7. 

 Megistocrinus evansi Keyea, 1890: Am. Naturalist, vol. XXIV, p. 254, pi. 



ix, fig. 1. 



Calyx very large, massive, subglobular, flattened somewhat 

 above. Basals three, of eqaal size, forming a flat, hexagonal 

 disk. Eadials of medium size, slightly wider than high ; first 

 and second costals a little smaller ; other calyx brachials about 

 the same size, except toward the bases of the free arms, where 

 they become very much shortened. Arms biserial, slender^ 

 bifurcating; pinnules long. Interradials sub-equal ; anal plate 

 like radials and in the same circlet, followed by three ossicles 

 in the second tier. Surface of plates unornamented ; usually 

 rounded slightly at the margins. Ventral side low, flattened 

 or slightly arched ; ossicles rather large, some of them tuber- 

 culose or sub- spinous. Anal aperture opening laterally at the 

 arm-basis. Stem long, ma8si^'e, round. 



Horizon and localities. — Lower Carboniferous, Burlington 

 Jimestone : Springfield. 



Megistocrinus brevicornls (Hall) 



Plate xxii, figs. 5a- b. 

 Actinocrinus brevieornis Hall, 1858: Geol. Iowa, vol. I, p. 571, pi. x, figs. 



4a-b. 

 Actinocrinus superlatus Hall, 1858 : Geol. Iowa, vol. I, p. 572. 

 Actinocrinus minor Hall, 1858: Geol. Iowa, vol. I, p. 573. 

 Megistocrinus brevico?-nis Wachsmuth & Springer, 1879: Proc. Acad. Nat. 



Sci., Phila., p. 311. 



Very similar to M. evansi, but very much smaller, seldom 

 attaining a measurement of the calyx of more than three-fourths 

 of an inch, while the other species is over two inches in 

 diameter. 



Horizon and localities . — Lower Carboniferous, lower 

 Burlington limestone : Louisiana. 



