36 BULLETIN 64, UNITED STATES NATIONAL MUSEUM. 



are also much smaller in proportion to the size of the radials, and the 

 elevation for the attachment of the column differs in being distinctly 

 circular in outline and uniform in thickness. Contrary to Troost's 

 observation, the lumen, in the only specimen which shows this 

 feature, is plainly circular. 



Formation and locality. — Brownsport limestone. Decatur County, 

 Tennessee. 



Cat. No. 39930, U.S.N.M. 



MARSIPOCRINUS STELLATUS (Troost). 



Plate 10, figs. 1, 2. 



Cupellsecrinit.es stellatus Troost, Proc. Amer. Ass. Adv. Sci., II (read 1849), 1850, 



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

 Cupellsecrinus stellatus Shumard, Trans. Acad. Sci. St. Louis, II, No. 2, 1866, 



p. 361 (catalogu ■ name). — Wachsmuth and Springer, Rev. Palseocrinoidea 



II, 1881, p. 230 (catalogue name). 



The original description is as follows. 



A pentagonal flat, disk, slightly depressed towards the center. The costals [radials] 

 lie in the same plane with the pelvis [base] only slightly elevated, so that the scapulars 

 [secundibrachs] and inter-costals [interbrachials] alone form the sides of the cup. 

 The arms and hands [arm bases] project considerably beyond the general circumfer- 

 ence which gives it the form of a star with five rays. The circular elevated ridge 

 round the cicatrice of the column, is surrounded with a pentagonal elevated border. — 

 Surface smooth, — coronal integument [tegmen] slightly elevated towards the center, 

 composed of smooth polygonal plates; oral [anal] aperture subcentral. The rows 

 of tubercles, mentioned in the description of C. verneuili, are visible in this species, 

 where they join the hands [arms]. 



Observations. — The calyx is hardly so Hat as indicated by Troost's 

 description, for the radials are bent upward and take part, at least in 

 their upper portion, in the formation of the dorsal cup. The arm 

 bases are protruding and deflected slightly downward from the hori- 

 zontal. Some portions of the surface show trace of radiating ridges, 

 but the. ornament has been nearly all removed by solution or silicifi- 

 cation. On the tegmen the ambtilacral plates are larger and less 

 easily distinguished from the interambulacrals than is the case with 

 Marsipocrinus verneuili. The plates of the tegmen are nearly flat 

 with the exception of a few of the ambulacrals which are slightly 

 nodose. 



This species is nearest to Marsipocrinus tennesseensis, but differs 

 in the presence of a distinct rim around the area for the attachment of 

 the column, the more prominent deflected arms, and the smooth in- 

 stead of nodose tegmen plates. 



Formation and locality. — Brownsport limestone. Perry or Decatur 

 County, Tennessee. 



Cat. No. 39929, U.S.N.M. 



