TKOOST'S CRINOTDS OF TENNESSEE E. WOOD. 



87 



Formation and locality. — St. Louis limestone. Near Huntsville, 

 Alabama; Maury County, Tennessee. 

 Cat. No. 39944, U.S.N.M. 



SCAPHIOCRINUS, species undetermined. 



Plate 6, fig. 5. 



Cyathocrinites planus (?) Troost, Proc. Amer. Ass. Adv. Sci., II (read 1849), 1850, 

 p. 61; MSS., 1850. 



The original description by Troost is as follows: 



The body of this crinoid and its column resembles the Cyathocrinites planus of Miller, 

 except that the scapulars have not the horse-shoe shape impression. It is impossible 

 from the present state of our fossil to say whether there existed any difference in the 

 construction of arms, hands, etc. 



It is partly imbedded in an argillaceous sandstone which lies above the aluminous 

 shale. This argilo-siliceous stratum has the appearance of chert or hornstone, at other 

 places it resembles more or less tripoli, and is sometimes used as such. Large tracts 

 of it pervade middle Tennessee in which no traces of organic remains can be found. 

 Again we find spots where Syringopora and Catenipora occur, and at other places we 

 find the rock entirely composed of several species of Fenestella amongst which are the 

 F. prisca and F. antiqua. In this deposit also the rich iron ores (hydroxide of iron) 

 of Middle Tennessee are situated. It is below the coal. M. Deverneuil considers it 

 as Devonian. 



Stewart County, Tennessee. 



Observations. — This specimen is embedded in the matrix with the 

 posterior interradius down, and only indistinct molds of the arm 

 plates showing. The infrabasals are large, pentagonal; basals hex- 

 agonal, about equal in length and width; radials wider than long and 

 truncated across their entire width for the reception of the arms. 

 These characters indicate the genus Scaphiocrinus, but from the con- 

 dition of preservation it is impossible to tell whether or not the speci- 

 men belongs to an already described species. 



The arms are not as large or as simple as represented in Doctor 

 Troost's figure, and the longitudinal ridges shown there are entirely 

 wanting in the specimen. The arms are apparently about half the 

 width of the radials, with strongly wedge-shaped plates, and they 

 seem to branch once or twice above the radials. The column plates 

 are circular, thin, and alternate in size. 



The specimen bears some resemblance to Poteriocrinus verus Miller 

 and Gurley, but the arm plates are shorter, the sides of the body 

 more curved, and it is probable that the arms branch below the fifth 

 or seventh plate above the radials. 



Formation and locality. — Keokuk horizon of the Tullahoma forma- 

 tion. Stewart County, Tennessee. 



Cat. No. 39949, U.S.N.M. 



