102 BULLETIN 64, UNITED STATES NATIONAL MUSEUM. 



of sides — pentagonal or hexagonal ; primaxil succeeded by two or three 

 secundibrachs which are separated by an elongate intersecundibrach. 



Interbrachial formula 1, 2, 2, 2. The first anal plate truncates the 

 posterior basal and is succeeded by two rows of three plates each. 

 The posterior basal with the succeeding anals form a straight longi- 

 tudinal row of hexagonal plates decreasing in size upward. 



The surface is without ornament except for the low nodes men- 

 tioned above and a faint ridge which begins at the upper margin of 

 the radials and traverses the radial series of plates becoming stronger 

 near the arm bases. The interbrachial and anal areas are not strongly 

 depressed. 



The tegmen, arms, and column are not preserved. 

 Upper stem joint circular, lumen pentalobate. 



Observations. — This species resembles the specimens figured by 

 Wachsmuth and Springer [1897, plate 18, figs. 6a~d], under the 

 name of Thysanocrinus inornatus, but it differs from them in lacking 

 the strongly elevated median row of anal plates and in the less pro- 

 nounced depressions between the arms. The present specimens are 

 also smaller than those figured by Wachsmuth and Springer. 



Formation and locality. — Brownsport limestone. Decatur and 

 Perry counties, Tennessee. 



Cat. Nos. 39968, 39979, U.S.N.M. 



Family LAMPTEROCRINIMD Bather. 

 Genus LAMPTEROCRINUS Roemer. 

 Balanocrinites Troost (not Agassiz 1845), Proc. Amer. Ass. Adv. Sci., II (read 



1849), 1850, p. 60 (nomen nudum) ; MSS., 1850. 

 Lampterocrinus Roemer, Die. Sil. Fauna des westl. Tenn., 1860, p. 37. — Hall, 

 Trans. Albany Inst., IV, 1863, p. 202.— Shumard, Trans. Acad. Sci. St. 

 Louis, II, No. 2, 1866, p. 378 (catalogue name).— Hall, 20th Rep. New York 

 State Cab. Nat. Hist., 1868, p. 328.— Zittel, Handb. d. Pal., I, 1879, p. 

 375. — Wachsmuth and Springer, Rev. Palseocrinoidea, II, 1881, p. 199. — De 

 Loriol, Pal. Francaise, XI (Crinoides), p. 59. — Wachsmuth and Springer, 

 Rev. Palseocrinoidea, III, 1885, p. 101. — Miller, North Amer. Geol. and 

 Pal. 1889, p. 257 (catalogue name). — Zittel, Text-Book Pal. (Eastman trans.), 



1896, p. 145. — Wachsmuth and Springer, North Amer. Crinoidea Camerata, 



1897, p. 207.— Bather, A Treatise on Zoology, III, The Echinoderma, 1900, 

 p. 199. 



The original description by Troost is as follows: 



generic characters. 

 Pelvis [base] pentagonal, divisible into five parts. 



Column pentagonal with circular alimentary canal [lumen] articulating surface 

 striated near the margin. 



Costals [basals] first series five, pentagonal, placed upon the five sides of the pelvis, 

 forming a pentagon with five re-entering angles. 



Second series [radials] five, heptagonal, placed in the re-entering angles of the 

 pentagon formed by the first series of costals [basals]. 



Scapulars [second primibrachs], five, pentagonal, the superior angle cut out for the 

 insertion of arms, which are placed upon the heptagonal [?] plates of the second series 

 of costals [primibrachs]. 



