498 PALEONTOLOGY OF ILLINOIS. 



Column near the base very thick, round, and, as usual in 

 the group, composed of very thin pieces, but tapering rap- 

 idly below. 



Surface of the figured specimen eroded so as not to show 

 the granules usually seen on the species. 



This is one of the few species of all those that have been referred, in 

 this country, to Forbesiocrinus, that really possess the characters distin- 

 guishing that group, most of the others having either only a single 

 range of anal pieces, like an arm, rising in the middle of the anal area, 

 with a kind of integument of minute pieces on each side, and thus be- 

 longing to the section Onychocrinus, or having one or two anals, and 

 one or two iuterradials, or sometimes none, and thus belonging to 

 the section Taxocrinus proper. In this species, as well as all other 

 typical forms of Forbesiocrinus, the anal and iuterradial areas are all 

 filled with well developed plates all the way up. We believe, however, 

 as elsewhere stated, that these three groups form only sections of the one 

 genus Taxocrinus. 



The species under consideration seems to be most nearly allied to F. 

 multibrachiatus, of Lyon and Casseday, (Am. Jour. Sci. and Arts, Vol. 

 XXVIII, p. 235, 1859), but has nearly twice the number of iuterradial 

 pieces to each area, and about five times as many anal pieces, as well 

 as about twenty more arms, or divisions of its rays. 



Locality and position This species was originally described by Prof. 

 HALL, from the Keokuk division of the Lower Carboniferous, at Keo- 

 kuk, Iowa, and we have it from the same horizon at Hamilton, Hancock 

 county, of this State. The very beautiful specimen we have figured is 

 from rocks of the same age at Crawfordsville, Indiana, and belongs to 

 the collection of Mr. COREY. As far as can be determined from an 

 eroded specimen, the example we have figured agrees well with those 

 from the Iowa and Illinois localities, excepting that its anal and inter- 

 radial areas are not sunken, but nearly even with the radial series. 

 This, however, may be in part due to the wearing away of the surface 

 of the latter. 



ONYCHOCBINTJS EXCULPTUS, L. and C. 



PI. 14, Fig. 4. 

 Onychocrinus exculptus, LYON and CASSEDAY, 1859. Amer. Jour. Sci., Vol. 29, new series, p. 78. 



Locality and position Keokuk group. The specimen here figured is 

 from Crawfordsville, Indiana. 



