NO. 1850. KN0B8T0NE CRINOTD FAUNA— SPRINGER. 187 



LIST OF THE KNOBSTONE CRINOIDEA. 

 GILBERTSOCRINUS Phillips. 



G. cf. tenuiradiatus Hall, Lower Burlington, Burlington, Iowa, 

 This is only a fragment, consisting of part of an interradial append- 

 age, rather delicate, ornamented with small, sharp tubercles on the 

 dorsal side, and, what is most important, having only two rows of 

 covering plates — a true Burlington type, never found in the Keokuk, 

 where all species have four. 



Locality. — Button-mould Knob. 



ERETMOCRINUS Lyon and Casseday. 



1. E. yandelli (Shumard). (Trans. Acad. Sci. St. Louis, vol. 1, 

 1860, p. 76.) Syn. E. prodigialis Miller and Gurley. (Bull. No. 7, 

 Illinois State Mus., 1895, p. 39.) 



Referred to Keokuk Group by all authors. I have the types in 

 the Lyon collection from Button-mould Knob, and good specimens 

 were found there and in neighboring knobs by Braun. Arm frag- 

 ments of some large Eretmocrinus were found in the same bed. This 

 well-known species was referred by Wacshsmuth and Springer to 

 Lohocrinus,^ to which I do not now agree; in the absence of the arms 

 which have not been found attached, it is difficult to place satisfac- 

 torily, but is more probably an Eretmocrinus. It has not the pro- 

 jecting basal rim of the genus generally, but this is true also of some 

 Lower Burlington forms, where the genus is represented, by several 

 species; and it ranges from the Kinderhook to the Keokuk. This spe- 

 cies has not been found except at the Kentucky Knobs. Miller and 

 Gurley described E. prodigialis upon a specimen of it from the type 

 locahty, unusually mature, and having abnormally a few extra 

 arms. This species has superficially more of a Keokuk aspect than 

 any of the others of the supposed Knobstone fossils. It is very large 

 for the genus, and has a rugose appearance from its highly tumid 

 plates both dorsally and ventrally; but these plates on the ventral 

 side, in well-preserved specimens, are found to be covered with a 

 distinct ornamentation formed by small raised tubercles, such as is 

 not usual in Keokuk forms. A number of specimens have been 

 found, all in the so-called "washes" at Button-mould and adjacent 

 knobs; but none at any true Keokuk locality. 



iocaZi^.— Button-mould and Jacobs Knobs, Kentucky; not found 

 at Whites Creek. 



2. E. praegravis IVIiller. 



3. E. ramulosus Hall. 



1 North American Crinoidea Camerata, 1S97, p. 441. 



