TROOST 's CRINOIDS OF TENNESSEE E. WOOD. 



43 



Genus PTEROTOCRINUS Lyon and Casseday. 



Codonicrinites Troost, Proc. Amer. Ass. Adv. Sci., II (read 1849), 1850 (nomen 

 nudum); MSS., 1850. 



Asteriocrinus Lyon (not Minister, 1839), Geol. Rep. Kentucky, III, 1857, p. 472. 



Pterotocrinus Lyon and Casseday, Amer. Jour. Sci. (2), XXIX, 1859, p. 68. — 

 Meek and Worthen, Geol. Rep. Illinois, II, 1866, p. 288. — Shumard, Trans. 

 Acad. Sci. St. Louis, II, No. 2, 1866, p. 394. — Wetherby, Journ. Cincinnati 

 Soc. Nat. Hist., II, 1879, p. 134.— Zittel, Handb. d. Pal., I, 1879, p. 365.— 

 Wachsmuth and Springer, Rev. Palaeocrinoidea, II, 1881, p. 87; III, 1885, 

 p. 120.— Miller, North Amer. Geol. and Pal., 1889, p. 276.— Wachsmuth 

 and Springer, North Amer. Crinoidea Camerata, 1897, p. 791. — Bather, A 

 Treatise on Zool., Ill, The Echinoderma, 1900, p. 159. 



The original description of Codonicrinites by Troost is as follows: 

 Generic characters. 



Pelvis [base] hexagonal divided into two equal parts. 

 Scapulars [radials] five, pentagonal deeply truncated. 

 Interscapular, one — conical. 



Arms, five — divided into four feathered hands which are separated four by four by a 

 solid plate originating upon the superior angle of the arm plates. a 

 Column, cylindrical. Alimentary canal [lumen] circular. 



PTEROTOCRINUS ACUTUS Wetherby. 



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

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



Pterotocrinus acutus Wetherby, Journ. Cincinnati Soc. Nat. Hist., II, 1879, 

 p. 134, pi. xie, figs. 2a, b, c. — Wachsmuth and Springer, Rev. Palaeo- 

 crinoidea, II, 1881, p. 91. — Miller, North Amer. Geol. and Pal., 1889, p. 

 276. — Wachsmuth and Springer, North Amer. Crinoidea Camerata, II, 

 1897, p. 799, pi. lxxix, figs. Za-g. 



Pterotocrinus spatulatus Wetherby, Journ. Cincinnati Soc. Nat. Hist., II, 1879, 

 p. 137, pi. in, fig. 3. 



Troost's description of this species is as follows: 



It has the form of a small bell or obtuse cone, having five broad projections around 

 the rim, from which proceed the arms, or considering the whole, with its superstruc- 

 ture, it resembles the ornaments known by the name of tassels. 



The hexagonal pelvis [base] is divided into two equal parts, the dividing line pro- 

 ceeding upwards [downward] from the inferior edge of one of the scapulars [radials], 

 traversing the alimentary canal [lumen], and terminating at the inferior margin of 

 the interscapular [radianal]. 



Scapulars [radials] five, — irregular pentagonal [hexagonal] deeply truncated on its 

 superior angle, forming a slightly concave excavation, in the middle of which is a 

 small polygonal plate which enters partly the superior edge of the large scapular 

 [radial] and partly the two small plates which are placed in the excavation before 

 mentioned. These small plates are joined together in such a manner as to form a 

 curve, upon which are placed four small flat quadrilateral plates, from each of which 

 proceeds a hand [arm]. 



From the summit of the above mentioned curve proceeds a solid plate, which ter- 

 minates at the superior extremity of the hands [arms], and divides them as is the 



a As long as we have pelvis, ribs, shoulders, arms, hands and fingers in the crinoids, 

 we of course must make use of these names, but it puzzles me often, as in this fossil 

 to distinguish an arm from a hand. As everything will be cleared up by the figures, 

 I hope the arms and hands will be found out. — Troost. 



