NO. 1S50. KNOBSTOXE CRINOID FAUNA— SPRINGER. 205 



SCHIZOBLASTUS Etheridge and Carpenter. 



This genus is closely related to the one commonly known as Gran- 

 atocrinus, a name which under the laws of priority now gives way to 

 Orhitremites, from which it was separated by Etheridge and Carpen- 

 ter. The two constitute essentially a Choteau-Burlington group, 

 only one small species being from the Keokuk; two species referred 

 to it by some authors from the St. Louis and Kaskaskia respectively 

 probably belong elsewhere. Seven species are recognized from the 

 Mountain Limestone of England, Ireland, and Belgium; and in this 

 country two have been described from the Choteau, five from the 

 Lower Burlington, six from the Upper Burlington, and one, the 

 smallest of the genus, from the Keokuk. Besides these is the well- 

 known and magnificent Granatocrinus granulosus of Roemer, by far 

 the largest of either of these genera, which, on account of having ten 

 spiracles instead of five, must be referred to Scliizoblastus. Its hori- 

 zon has been involved in a curious lot of guesswork. Roemer, in 

 describing \V, gave as its localities, on the authority of Troost and 

 Shumard, Shelbyville, Bedford County, Temiessee, and Allen County, 

 Kentucky; and the horizon simply as Kohlenkalk. It is referred to 

 the St. Louis by Etheridge and Carpenter,- by S. A. Miller,^ and by 

 Weller.* Shumard in his Catalogue^ referred it to the Kaskaskia; 

 while Troost, who described it in his Monograph, unpublished until 

 lately, said it was from the Devonian." With all this lucid informa- 

 tion in the literature to choose from, the collectors have taken another 

 guess at it. I have specimens of this species obtained in various 

 collections, from Bradfordsville, Sallietown, and other localities in 

 Marion County, Kentucky, Whites Creek and Maury County, Ten- 

 nessee; and they are without exception labeled Keokuk. Now it is 

 significant that every one of these localities, as well as those given 

 by Troost, Roemer, and Shumard, is in a region where the shales 

 pass up from the Devonian to the Lower Carboniferous Limestone, 

 and where the lower member of Safford's ''Siliceous Group" — i. e., the 

 Knobstone — is exposed; and also that no specimen of this species has 

 ever been reported from any typical Keokuk locality. To all. this I 

 am now able to contribute one decisive fact — namely, good specimens 

 direct from the Knobstone shales at Stone's farm, Clark County, 

 Indiana, in layers 40 or 50 feet above the Black Slate, and where 

 there is no Keokuk mingled in the debris. Troost's reference to the 

 Devonian undoubtedly meant these same shales, and the conclusion 



1 Monogr. Blastoidea, p. 43. * BuU. 153, U. S. Geol. Surv., p. 299. 



2 Cat. Blastoidea, p. 214. s Trans. St. Louis Acad. Sci. vol. 2, p. 375. 



3 North Amer. Geol. and Pal., p. 250. s BuU. 64, U. S. Nat. Mus., p. 21. 



