20 8 PALAEONTOLOGY OF ILLINOIS. 



provided with a shallow sinus, equaling about half the breadth 

 of the plate. Second radial pieces very small, near half as 

 long as wide, and supporting on their superior sloping concave 

 sides, the first divisions of the arms. Interradial plates com- 

 paratively large for a species of this genus, and each provided 

 with a short central spine. Anal plate unknown. 



Arms slender, after the first divisions on the small second 

 radials, bifurcating again on the second piece, and above this 

 the two inner branches divide once more on the second 

 piece, making apparently six arms to each ray. All the 

 divisions of the arms, above the last bifurcation, at first 

 composed of a single series of wedge-formed pieces, but gradu- 

 ally passing into double alternating series. Below the bifur- 

 cation all the joints are nearly or quite as long as wide, con- 

 stricted around the middle, and provided with prominent late- 

 ral projections at the upper and lower ends; all supporting 

 tentacles, even down to the first pieces above the second 

 radials. Column rather small, compressed, and composed of 

 nearly equal, short segments, near the body. Height, to sum- 

 mit of first radial plates, 0.42 inch; breadth, 0.57; breadth 

 of base, 0.44 inch; height of do., 0.15 inch. 



One of the most marked peculiarities of this crinoid, is the globose form of 

 its body, which is distinctly gibbous in the middle, and rounded above, as well 

 as below ; its arms are also rather unusually slender in proportion to the size 

 of the body. 



Locality and position : Same as last. 



Genus TAXOCRINUS, Phillips. 



Si/non. — Poteriocrinus? and Cyathocrinus? (sp.), Phillips, 1836. Geol. Yorksh., part ii; 



(not Miller, 1821). 

 Isocrinus, Phillips, 1841. Palaeozoic Fossils, p. 30; (not von Meyer, 1837). 

 Cladocrinus, Austin, 1842. Ann. Mag. Nat. Hist.., vol. x; (not Agassiz, 1834). 

 Taxocrinus, Phillips, 1843. Morris Cat. British Fossils, p. 90 ; McCoy, 1844, 



Carb. Fossils, Ireland, p. 178; and 1851, Brit. Pal. Foss., p. 53. 

 Forbesiocrinus, de Koninck and Lehon, 1854. Rech. Crin. Carb., Belgique, 



p. 118. 



