88 



BULLETIN 64, UNITED STATES NATIONAL MUSEUM. 



Family SCYTALOCRINIDiE Bather. 

 Genus SCYTALOCRINUS Waehsmuth and Springer. 



SCYTALOCRINUS (?) GRACILIS (Troost). 



Plate 11, fig. 9. 



Agassizocrinites gracilis Troost, Proc. Amer. Ass. Adv. Sci., II (read 1849), 1850, 



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

 Scaphiocrinus gracilis Hall, Rep. Geol. Surv., Iowa, I, Pt. 2, 1858, p. 551. 

 Agassizocrinus gracilis Shumard, Trans. Acad. Sci. St. Louis, II, No. 2, 1866, p. 



352 (catalogue name). — Wachsmuth and Springer, Rev. Palseocrinoidea, 



III, 1886, p. 265 (catalogue name).— Miller, North Amer. Geol. and Pal., 



1889, p. 221 (catalogue name). 



The description by Troost is as follows: 



The general form of this crinoid is that of an inverted cone — composed of smooth 

 plates. 



Pelvis [infrabasals] five? triangular — superior margin more or less convex, so as to 

 form, when joined together, a cup having five slightly reentering angles. No trace 

 of the insertion of a column is visible at the base. 



Costals [basals], five subpentagonal. They are placed in the slightly re-entering 

 angles of the pelvis [base]. 



Scapulars [radials] five, subquadrilateral — they are placed in the reentering angles 

 of the costals [basals] and support: — 



Arms [primaxils] — five — they are more or less cylindrical, contracted in the middle 

 and terminate in a cuneiform summit which supports two hands. 



The capital integument seems to have been much elevated towards the centre, and 

 was covered with polygonal plates. In my specimen the external surface is eroded 

 and shows the joints of the plates of this capital integument from which it appears 

 that they were surrounded by numerous spines intruding between those of the adjoin- 

 ing plates. This integument, as far as I can judge from my specimen, is larger than the 

 whole body, from its base to its scapulars. 



Occurs in the base of the Cumberland Mountains, Tenn., and in the vicinity of 

 Hunts ville, Alabama. 



Observations. — This species was referred by Troost to the genus 

 Agassizocrinus on account of the absence of a column, but it differs 

 from Agassizocrinus in the smaller size of its infrabasals, in having 

 basals smaller than radials, and radials truncated across their entire 

 upper margin for the reception of the arms. The sutures between 

 radials and primibrachs are gaping. 



In these and in other features, except in the absence of a column, 

 the specimen shows the characters of Scytalocrinus Wachsmuth and 

 Springer. There is but one individual of the species in the collection, 

 and the absence of a column in this case is believed to be accidental. 

 The plates of the anal area and of the left postero-lateral ray are 

 much distorted; hence it is probable that the crinoid lost its stem 

 when young and lay on its side as it grew, producing the irregularity 

 observed in the plates of that side. Four of the infrabasals meet in 



