76 



BULLETIN 64, UNITED STATES NATIONAL MUSEUM. 



LOBOCRINUS ROBUSTUS Wachsmuth and Springer. 



Actinocrinites hplbrooki Troost, MSS., 1850. 



Lobocrinus robustus Wachsmuth and Springer, North American Crinoidea 

 Camerata, 1897, p. 436, pi. xxx, figs. 8a, 6— Weller, Bull. No. 153, U. S. 

 Geol. Surv., 1898, p. 333. 



The following description is by Troost: 



This crinoid has the form of two cones joined base to base, from the junction of which 

 project five large arms, which convert the circular rim of the cones into a pentagon 

 and give it the appearance, when a top or bottom view is taken, of a star with obtuse 

 rays. The plates covering the cup are smooth and more or less elevated in the centre. 

 Those that cover the capital integument are tumid, projecting almost hemispherically 

 above the surface. The capital integument (the superior cone) is more elevated and 

 larger than the inferior one and terminates in a large proboscis, the superior extremity 

 of which is wanting in my specimen. 



Decatur County, Tennessee, Silurian. 



Observations. — This species is represented in the Troost collection 

 by a single young individual, which is fairly well preserved. 



Formation and locality. — Keokuk horizon of Tullahoma formation. 

 White's Creek Springs, Decatur County, Tennessee. 



Cat. No. 39901, U.S.N.M. 



Family PERIECHOCRINID^ Bather. 

 Genus PERIECHOCRINUS Austin. 



PERIECHOCRINUS TENNESSEENSIS (Hall). 



Plate 6, fig. 10. 



Crumenxcrinites ovalis Troost, Proc. Amer. Ass. Adv. Sci., II (read 1849), 1850, 



p. 62 (nomen nudum); MSS., 1850. 

 Actinocrinites tennesseex (in part), Troost, MSS., 1850. 



Saccocrinus tennesseensis Hall, Geol. Rep. Ohio, Pal., II, 1875, p. 125, pi. vi, 

 fig. 10. — Wachsmuth and Springer, Rev. Palseocrinoidea, II, 1881, p. 236 

 (catalogue name). — Miller, North Amer. Geol. and Pal., 1889, p. 279 (cata- 

 logue name). 



Periechocrinus tennesseensis Wachsmuth and Springer, North Amer. Crinoidea 

 Camerata, 1897, p. 528. 



The following description of Actinocrinites tennesseese is by Troost: 



Its external form is that of an elevated goblet with a low, dome-shaped capital 

 integument. 



It differs from the generality of Actinocrinites in the dimensions and form of the 

 proboscis which in the true Actinocrinites diminishes gradually in diameter from its 

 base to its summit, whereas in the A. tennesseese it is already of a small diameter when 

 it rises above the integument. 



The large figure is very imperfect as to the arrangement of its plates — the small 

 figure [pi. 6, fig. 10 J is a perfect representation. 



Observations. — Hall's description of this species contains a reference 

 to Troost's manuscript description, but according to the rules of 

 priority the species should be accredited to Hall. 



