TROOST 's CRINOIDS OF TENNESSEE E. WOOD, 



83 



Observations. — This species is referred with much doubt to the 

 genus Cyathocrinus. The radials are now separated, but whether 

 this separation is due to compression or whether interbrachials were 

 formerly present can not be determined from the specimen. 



The specimen may be compared with species of Botryocrinus in 

 the form of the dorsal cup and the arrangement of the plates on the 

 anterior side. The posterior side is imbedded in the matrix, hence 

 it is impossible to determine the presence or absence of a radianal. 



The arms show no trace of the stronger rami characteristic of 

 Botryocrinus, but instead the lateral bifurcations are equal in size 

 with a greater number of brachials in "the admedian branch of the 

 dichotom," as described by Bather for the genus Cyathocrinus. The 

 species is referred to Cyathocrinus more from the character of the 

 arms than from the calyx, which is too poorly preserved to define the 

 position of the species. 



Formation and locality. — St. Louis limestone, Lawrence County, 

 Tennessee. 



Cat. No. 39937, U.S.N.M. 



Suborder DENDROCRINOIDEA Bather. 



Family DENDROCRINIDiE Bather. 

 Genus DENDROCRINUS Hall. 



DENDROCRINUS POLYDACTYLUS (Shumard). 



Homocrinus polydactylus Shumard, Trans. Acad. Sci. St. Louis, I, 1857, p. 78, 



pi. i, fig. 6; II, No. 2, 1866, p. 378 (catalogue name). 

 Cyathocrinites conglobatus Troost, Proc. Amer. Ass. Adv. Sci., II (read 1849), 



1850, p. 61 (nomen nudum); MSS., 1850. 

 Dendrocrinus polydactylus Meek, Geol. Surv. Ohio, Pal., I, 1873, p. 22, pi. in, 



bis., fig. 9. — Wachsmuth and Springer, Rev. Palseocrinoidea, I, 1879, p. 77 



(catalogue name). — Miller, North Amer. Geol. and Pal., p. 239 (catalogue 



name). 



The description by Troost is as follows : 



Pelvis unknown — It is small, inserted in a deep cavity, supported by a cylindrical 

 column. Costals [infrabasals] composed of almost spherical plates, laterally com- 

 pressed — the superior part cuneiform. Scapulars [basals] placed in the re-enter- 

 ing angles of the costal series [infrabasals], are very tumous, their superior margin is 

 cuneiform supporting two bifurcated arms. 



It is spread out over limestone entirely composed of Orthis [Dalmanella] testudinaria, 

 Leptena [Rafinesquina] alternata and others. 



Occurs in the vicinity of Nashville, Davidson County, Tennessee, and in the State of 

 Ohio. 



Observations. — The radials of this species are somewhat crushed 

 and displaced, and Doctor Troost has evidently mistaken the basals 

 for radials, assuming the existence of a circle of minute plates below 

 the true infrabasals, The latter are large and tumid plates. 



