Paleontology of the Cincinnati Group. in 



more ; tertiary radials, when present, also variable, separate 

 or united according- to the age of the specimen ; arms 20, 

 rising almost vertically from the last radial, long, slender, 

 simple from the second division, rounded on the outer side, 

 and composed of a single series of short, somewhat wedge- 

 shaped pieces, each one of them supporting, at its larger end, 

 a pinnule; pinnules very slender, alternately and very closely 

 arranged, proximal ones fixed in the body walls, the first 

 generally given off from the second secondary radials ; inter- 

 radial areas occupied by a large number of pieces, arranged 

 in 4 or more series, with 1 plate in the first, 2 in the second, 

 and generally 3 in each succeeding series; the anal area 

 differs from the others in being a trifle wider, and in hav- 

 ing 3 instead of 2 plates in the second and all succeeding 

 series; inter axillary plates from 1 to 10; vault scarcely 

 elevated above the horizon of the arm bases; interradial 

 regions somewhat depressed, and composed of numerous 

 very small convex plates; anal aperture directly through 

 the vault, eccentric ; column round, medium size ; central 

 canal small, distinctly pentagonal. (Pal. New York, Vol. I, 

 p. 280; Wachsmuth & Springer, Review of Palaeocrinoidea, 

 Part 2; (Proc. Phila. Acad. Nat. Sci. for 1881), p. 187.) 



(Pycnocrinus S. A. Miller, 1883, Jour. Cin. Soc. Nat. Hist., 

 Vol. VI, p. 231.) 



Remarks. — Originally proposed by Hall in 1847. A number 

 of species have been placed in this genus. The revised and 

 restricted definition given above is that of Wachsmuth & 

 Springer. Pycnocrinus is placed by them as a synoinm 

 formed, they believe, on a young Glyptocrinus. 



1. — G. decadactvlus Hall, 1847. 



Body obconoidal, with interradial and axillary areas a little 

 flattened, so as to present a pentagonal outline ; somewhat 

 wider than high ; under-basals undeveloped ; basals small 

 pentagonal, wider at the top than high; first radials larger 

 than basals, as wide as high, heptagonal ; second radials a 

 little smaller than the first, hexagonal or heptagonal ; third 

 radials same size as second heptagonal and each supporting 

 2 secondary radials, each nearly as large as the third primary 



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