18 BULLETIN 64, UNITED STATES NATIONAL MUSEUM. 



It is the only species of the Tennessee Pentremites which belongs exclusively to the 

 Silurean Strata. 



Decatur County, Tennessee. 



Formation and locality. — This species marks the middle, or Troos- 

 tocrinus zone, of the Beech River formation of the Brownsport lime- 

 stone, as defined by Pate and Bassler [1908]. 



Cat. No. 33071, U.S.N.M. 



Family NUCLEOCRINID^ Bather. 

 Genus NUCLEOCRINUS Conrad. 



Nucleoainus Conrad, Journ. Acad. Nat. Sci. Phila., VIII, 1842, p. 280. — Lyon 

 and Casseday, Proc. Amer. Acad., IV, 1859, p. 295. — Hall, 15th Ann. Rep. 

 New York State Cab. Nat. Hist., 1862, pp. 144, 146.— Meek and Worthen, 

 Rep. Geol. Surv. Illinois, II, 1866, p. 275. — Billings, Amer. Journ. Sci. (3), 

 I, 1870, p. 229.— Miller, North Amer. Geol. and Pal., 1889, p. 262.— Bather, 

 List Blastoidea Brit. Mus. (Nat. Hist.), 1899, p. 21 (catalogue name); A 

 Treatise on Zool., Ill, The Echinoderma, 1900, p. 88. 



Olivanites Troost, Proc. Amer. Ass. Adv. Sci., II (read 1849), 1850, p. 62 (nomen 

 nudum); MSS., 1850; Amer. Journ. Sci. (2d ser.), VIII, 1849, p. 419.— 

 Hambach, Trans. Acad. Sci. St. Louis, XIII, 1903, p. 48. 



Elaeacrinus Roemer, Archiv. f. Naturg., Jahrg. XVII, I, 1851, p. 375; Bronn's 

 Lethaea Geogn., 3rd ed., Pt. 2, 1852-54, p. 283. — Dujardin and Hupe, 

 Hist. Nat. Zooph. Ech., 1862, p. 100.— Shumard, Trans. Acad. Sci. St. 

 Louis, II, No. 1, 1862, p. Ill; II, No. 2, 1866, p. 368.— Etheridge and Car- 

 penter, Ann. and Mag. Nat. Hist., XI, 1883, p. 228; Cat. Blastoidea Brit. 

 Mus., 1886, p. 210.— Zittel, Textbook Pal. (Eastman trans.), 1896, p. 195. 



The original description by Troost is as follows: 



When I first saw this fossil, it being partly imbedded iu limestone, I considered it 

 as a species of Pentremites, having five double rows of pores, and five double apertures 

 at the summit like the Pentremites. I conjectured nevertheless that the lower part of 

 the animal, the place of insertion of a column, and the plates composing the pelvis 

 [base] differ from those of the genus Pentremites. The specimens then in my posses- 

 sion did not allow me to decide this point. I think it necessary to mention this as the 

 fossil is generally known, on my authority, (though I did not publish a description of 

 it) as a Pentremites. Having since got possession of perfect specimens, I have found 

 out my mistake. I am now convinced that it is not supported by a column, conse- 

 quently it constitutes a new genus, to which from the analogy of its form with that of 

 an olive, I have given the name of Olivanites. 



NUCLEOCRINUS VERNEUILI (Troost). 

 Plate 3, figs. 7, 8, 9, 10, 11, 12, 13. 



Pentremites verneuili. Troost, 6th Rep. Geol. State Tennessee, 1841, p. 14. — 



D'Orbigny, Prod, de Pal. Strat., I, 1849, p. 102.— Shumard, Trans. Acad. 



Sci. St. Louis, I, No. 2, 1858, p. 247. 

 Olivanites verneuili Troost, Proc. Amer. Ass. Adv. Sci., II (read 1849), 1850, p. 



62 (catalogue name); MSS., 1850.— Lyon, Rep. Geol. Surv. Kentucky, III, 



1857, p. 487, pi. v, figs. la-d. 

 Elaeacrinus verneuili Roemer, Archiv. f. Naturg., Jahrg. XVII, I, 1851, p. 379, 



pi. viii, figs, la-d; Bronn's Lethaea Geognostica, 3d ed., Pt. 2, 1852-54, 



