TROOST 's CRINOIDS OF TENNESSEE E. WOOD. 



73 



arm bases. Their form also agrees closely with that of D. euconus 

 var. abscissus Rowley and Hare, but that species has thirty-two arms 

 while D. sacculus has but eighteen. 



The mold of the interior figured on plate 5, figs. 4-6, is interesting 

 as showing casts of the ambulacra and arm openings in relief. The 

 arrangement of the calyx plates is shown more distinctly by the mold 

 than by some of the actual calyces. The depressions on the mold, 

 mentioned by Doctor Troost, seem to indicate that the interior of each 

 plate was convex and bore at its center two or more very slender, later- 

 ally compressed spines. 



Batocrinus sacculus Miller has been referred to Dizygocrinus since 

 it possesses the characteristic features of that genus in the low dorsal 

 cup, high tegmen, short basals with projecting circular rim, slender 

 anal tube, etc. 



Formation and locality. — Keokuk horizon of the Tulkthoma forma- 

 tion. White's Creek Springs, Davidson County, and Stewart County, 

 Tennessee; Washington County, Indiana. 



Cat. Nos. 39897, 39898, U.S.N.M. 



DIZYGOCRINUS UNIONENSIS (Worthen). 



Actinocrinites mortonii (in part) Troost, Proc. Amer. Ass. Adv. Sci., II (read 



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

 Actinocrinus mortoni Shumard, Trans. Acad. Sci. St. Louis, II, No. 2, 1866, p. 346 



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



1881, p. 225 (catalogue name). 

 Batocrinus unionensis Worthen, Bull. No. 2, Illinois State Museum Nat. Hist., 



1884, p. 26.— Miller, North Amer. Geol. and Pal., 1889, p. 228 (catalogue 



name). — Worthen, Geol. Rep. Illinois, VIII, 1890, p. 84, pi. xn, figs. 5, 



5a; pi. xiii, fig. 3. 



Batocrinus pulchellus Miller, Adv. Sheets 17th Geol. Rep. Indiana, 1891, p. 68, 

 pi. xi, figs. 13, 14. 



Batocrinus davisi Rowley and Hare, Kansas City Scientist, 1891, p. 116, pi. in, 

 fig. 9. 



Dizygocrinus unionensis Wachsmuth and Springer, North Amer. Crinoidea 

 Camerata, 1897, p. 424, pi. xxxv, figs. 16, 17, 18, 19, 20.— Weller, Bull. 

 No. 153, U. S. Geol. Surv., 1898, p. 235 (catalogue name). 



Observations.— Of the two specimens in the Troost collection 

 labeled Actinocrinites mortonii one is evidently Dizygocrinus unionensis 

 (Worthen), while the other represents the variety divalis (Miller). 

 Doctor Troost' s description and figure evidently apply to the latter 

 and are reproduced under that name. The variety differs from the 

 species in being larger and in having the arms double from their 

 point of origin. 



Full descriptions with figures of the species have been given by 

 Worthen [1884 and 1890] and Wachsmuth and Springer [1897]. 



Formation and locality. — Warsaw limestone. Hunts ville, Ala- 

 bama; Tate ville, Pulaski County, Kentucky; Boonville, Missouri; 

 Lee County, Virginia. 



Cat. No. 39985, U.S.N.M. 



