TROOST *S CRINOIDS OF TENNESSEE — E. WOOD. 105 



Supplementary description. — There are five large infrabasals, and 

 five thick basals, truncated across their upper margins. These are 

 the largest of the plates preserved. Radials quadrangular, their 

 inner surface traversed by two sharp ridges with rounded hollows 

 between them. These ridges start from near the proxinal margin 

 of the plates and diverge slightly toward the outer margin, where 

 they are about one third the width of the plates apart. The outer 

 surface of the radial bears a long spine, about 2 mm. in diameter 

 at its base. The one uncovered from the matrix was broken off at 

 a length of about 3 mm. The upper margin of the radial is crenulate 

 but it is difficult to determine how much of this crenulation may 

 have been produced by fracture or solution. 



Observations. — The genus seems to be related to Gilbertsocrinus, 

 but differs from it in the peculiar form of the basals and radials. It 

 is recorded from a horizon much lower than that of any described 

 species of Gilbertsocrinus. On the whole the fossil is a puzzling one 

 and too poorly preserved for an altogether satisfactory determination 

 of its affinities. 



SIDEROCRINUS ORNATUS Troost. 



Plate 12, fig. 7. 

 Siderocrinites ornatus Troost, MSS., 1850. 

 The name ornatus refers to the two diverging ridges on the interior 

 of the radials and the fluted character of their distal margins. 



Formation and locality. — Brownsport limestone. Decatur County, 

 Tennessee. 



Cat, No. 39935, U.S.N.M. 



Class STELLEROIDEA Gregory. 



Genus PALAEASTER Hall. 



PALAEASTER ANTIQUA (Troost). 



Plate 8, fig. 1. 



Asterias antiqua Troost (not Hisinger 1837), Trans. Geol. Soc. Pennsylvania, 



I, 1835, p. 232, pi. x, fig. 9; Proc. Amer. Ass. Adv. Sci., II (read 1849), 1850, 



p. 59 (catalogue name). 

 Petraster antiqua Shtjmard, Trans. Acad. Sci. St. Louis, II, No. 2, 1866, p. 386 



(catalogue name). 

 Palaeaster (Argaster) antiqua Hall, 20th Rep. New York State Cab. Nat. Hist., 



rev. ed., 1870, p. 329. 

 Palaeaster ant,iquus Miller, North Amer. Geol. and Pal., 1889, p. 265 (catalogue 



name). 

 Argaster antiqua Gregory/ Geol. Mag., 4th dec, VI, 1899, p. 345 (gen. ref.). 

 The following description is by Troost: 



I described the Asterias antiqua in a memoir read before the Geol. Soc. of Pennsyl- 

 vania, which was published in the transactions of that society in April, 1834 (vol. 1, 

 pag. 232). Since that time two naturalists have given the name of Asterias antiqua 

 to different species of Asterias — Hisinger in his Lethaea Sveciaca Holmiae 1837 pag. 

 89 Tab. 26, fig. 6, and Professor Locke of Cincinnati. (I do not recollect where 



