1SG PALAEONTOLOGY OF ILLINOIS. 



analogy, it was probably, as in Poteriocrinus, produced upwards as a large pro- 

 boscis. 



If the type of Graphiocrinus, de Koninck and Lehon, as suggested by Mr. 

 Lyon and Dr. Shumard, should be found to have five minute basal pieces 

 within the range described as basals by de Koninck and Lehon, it is not im- 

 probable that the group under consideration may be so connected with that type, 

 through such forms as the typical species of Scaphiocrinus, that it will become 

 necessary to unite the whole as members of one group. If so, de Koninck and 

 Lehon's name would have to stand for the entire group, unless Grapkiocrinus 

 and Zeacrinus should both be regarded as forming distinct subgenera under 

 Poteriocrinus. 



So far as known to us, the Zeacrinus group is confined to the Carboniferous 

 rocks ; though Prof. Hall has described two species he refers to this genus 

 from the Waverly Sandstone of Ohio, regarded by some as belonging to the 

 Upper Devonian. 



Zeacrinus Troostanus, M. and W. 



PI. 16, Fig. 2. 



Zeacrinus Troostanus, Meek and Worthen, September, 1860. Proceed. Acad. Nat. Sci., 



Philad., p. 390. 

 Zeacrinus scoparius, Hall, Feb., 1861. Descr. Crin. (Prelim. Notice, Albany), p. 8. 



Body depressed, basin-shaped below the arms, rounded and 

 concave on the under side; composed of apparently smooth 

 plates, which are connected by linear sutures. Base, small, 

 concave, and nearly or quite hidden by the column. Subra- 

 dial pieces unequal in size, a little wider than long, excepting 

 the largest one on the anal side, four of them hexagonal, and 

 one or two heptagonal, (counting three angles at the base). 

 First radials nearly twice as wide as high, pentagonal, the 

 superior horizontally truncated edge being longer than either 

 of the inferior sloping sides. Second radials about the size of 

 the first, wider than high, pentagonal, and indistinctly hexag- 

 onal; all longer on the inferior truncated side than either of 

 the others; apparently four of them supporting on their supe- 

 rior sloping sides the first divisions of the arms, while the fifth 

 on the anterior side is truncated above, and succeeded by three 



