Paleontology of the Cincinnati Group. 101 



Basals, 5, very irregular; radials, 5, very unequal; brach- 

 ials irregular in number; column round, luberculated. 



11. — Anomaeocrinus. 



Under basals, 5 ; basals, 5 ; column round, nearly smooth. 



12. — Merocrinus. 



Basals, 5 ; column round or pentagonal ; pinnules wanting. 



13. — Dendrocrinus. 



Genus i— RETEOCRINUS Billings, 1859. 



Calyx obconical, somewhat bilateral; interradial and inter- 

 axillary spaces depressed ; radial plates elevated into strong, 

 rounded ridges, resembling arms; they bifurcate and follow 

 the secondary radials, thence passing into free-arm joints; 

 underbasals 5, well developed; basals 5, large, protuberant, 

 hexagonal, the upper side slightly truncate, and supporting 

 the first series of interradial plates; radials 3 x 5> those of 

 the different rays separated by interradials : the first and third 

 pentagonal, second quadrangular; as long as, but narrower 

 than the two former; radials highly elevated, forming a 

 broad, rounded ridge, branching from the third radials up- 

 ward, following the secondary radials, and downward from 

 the first primary radials to the basals ; secondary radials, 4 to 5 

 in the adult, less in young specimens, quadrangular, decreas- 

 ing in height upward, shaped like arm joints, and giving off 

 pinnules; arms 10 to 24 long, slender, rounded, bifurcating, 

 composed of a single series of rectangular or slightly wedge- 

 shaped pieces, which give off on alternate sides rather stout, 

 closely-arranged pinnules ; i?iterradial series resting directly 

 on the basals, consisting of a very large number of minute 

 pieces, irregular in shape and without definite arrangement; 

 the posterior area wider, with a conspicuous row of decidedly 

 larger and more prominent special anal pieces along the me- 

 dian part ; interaxillary plates almost as numerous as the 

 interradials, and similar in character ; vault composed of nu- 

 merous, very small and convex pieces, with an elevation run- 

 ning to each arm base; anal aperture directly through the 

 vault, small, sub-central ; column sub-pentagonal ; central 



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