NO. 1850. KN0B8T0YE CRINOTD FAU\A— .SPRINGER. 195 



typical Keokuk at Crawfordsville and Indian Creek, and they are 

 much smaller than this, as are also those of the Upper Burlington. 

 This is the largest species of the genus, and it has been thought 

 that this makes for the Keokuk character of the horizon. But the 

 fact is that the course of this genus was one of degradation and 

 gradual extinction of natality. It represents a high speciahzation, 

 which began in the Devonian \\dth Mycocrinus of the Eifel and per- 

 sisted through this genus into the St. Louis, where its last representa- 

 tive, as found at HuntsviUe, Alabama, is a depauperate form of 

 very diminutive size. Therefore it is perfectly in accord \vith the 

 facts to consider that the line of development cuhninated in size with 

 the present species in the marls of the Ivnobstone, not later than the 

 age of the Lower Burlington. 



CYATHOCRINUS Miller. 



This is a genus of wide geographical distribution and long life. It 

 is a form of simple organization and generalized t^'pe, its calyx con- 

 sisting of mfrabasals, basals, radials, and an anal plate, just as we 

 find m the larva of some Antedons to-day. It ranges from the Siliu'ian 

 to the end of the Keokuk. It underwent slight changes with time, 

 and ran its course to extinction without any extravagant develop- 

 ment, as is usually the case with the simpler types. Except by the 

 color, and character of the matrix, it is hard to distinguish between 

 a smooth Cyathocrinus of the Burlington and one from the Keokuk. 

 About 10 species are recognized from the Silurian, chiefly from Got- 

 land; true Ci/athocrinus has not been noted in the Devonian, but its 

 acme came in the Lower Carboniferous, from wliich there have been 

 described species referable to the genus as follows: Mountam Lime- 

 stone of England, 9; Kinderhook, 1; Choteau, 1; Lower Burling- 

 ton, 7; Upper Burlington, 6; Keokuk, 18; from which numbere 

 some deduction must be made for synonyms, especially m the Keokuk. 

 The species described and listed from the St. Louis, Maxville Group 

 ( = Kaskaskia) , and Lower and Upper Coal Measures do not belong 

 to this genus. 



Cyathocrinus was evidently a very prominent crinoid in the Knob- 

 stone formation, and flourished in profusion in a variety of beautiful 

 forms, most of them higlily ornamented; several of them are unde- 

 scribed. The Lower Burlington described species are mostly small, 

 and a majority of them smooth. The ornamented ones, or some of 

 them, are represented or closely paralleled by species at some of the 

 Knobstone locahties. My material from the Knobs consists chiefly 

 of isolated plates; but by separating thesainto weU-defined groups 

 and reconstructing some caHces in part, it is sufficient to indicate the 

 existence of at least 8 weU-marked species, and to afford a good descrip- 

 tion of them by which they can be readily identified. Most of these 



