TROOST 's CRINOIDS OF TENNESSEE E. WOOD. 



37 



MARSIPOCRINUS ROS^FORMIS (Troost). 



Plate 13, figs. 5, 6. 



Cupellxcrinites rosxformis Troost, Proc. Amer. Ass. Adv. Sci., II (read 1849), 



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

 Cupellxcrinus rosxformis Shumard, Trans. Acad. Sei. St. Louis, II, No. 2, 1866, 



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



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



The original description is as follows: 



A circular disk more or less angular produced by the lateral projections of the inter 

 scapulars [interbrachials] Pelvis [base], costals [radials], scapulars [primibrachs] and 

 arms lie in the same plane — the interscapulars [interbrachials] only more or less ele- 

 vated, so that the hands [arms] seem to have immediately descended [extended lat- 

 erally]. Lower surface smooth [?] — alimentary aperture [lumen] pentalobate, coronal 

 integument [tegmen] hemispherical, composed of tumid polygonal plates. Oral [anal] 

 aperture subcentral. 



In this species the rows of tubercles [tumid ambulacral plates] so conspicuous in the 

 C. verneuili make their appearance near the circumference where they are divided 

 into four rows and seem to penetrate or join the hands [arms]. This is another beau- 

 tiful species of this genus. 



Observations. — The surface ornament consists of fine irregular ridges 

 radiating from the center of the upper margin of the radials and from 

 the transverse ridge across the interbrachials. The sutures are 

 sunken in narrow but deep grooves. The interbrachials are flat 

 below and convex above; the tegminal portion bends upward at a 

 sharp angle from the flat surface which forms a part of the calyx. 



This species is distinguished from others of the genus by the ex- 

 tremely flat calyx and the protruding interbrachials. The latter 

 give the calyx a ten-sided outline, forming five angles between those 

 of the arm bases. 



The specimens figured by Wachsmuth and Springer [1897, pi. 75, 

 figs. 16a, b], and identified with Marsipocrinus tennesseensis Roemer 

 resembles M. rosxformis in form and surface ornament, but the 

 sutures are described as not sunken and difficult to distinguish. Not- 

 withstanding this difference the figures seem to indicate a specimen 

 more nearly related to M. rosseformis than to M. tennesseensis. 



Formation and locality. — Brownsport limestone. Perry County, 

 Tennessee. 



Cat. No. 39932, U.S.N.M. 



MARSIPOCRINUS PENT AGON ALIS (Troost). 



Cupellxcrinites pentagonalis Troost, Proc. Amer. Ass. Adv. Sci., II (read 1849), 



1850, p. 61 (nomen nudum). 

 Cupellxcrinus pentagonalis Shumard, Trans. Acad. Sci. St. Louis, II, No. 2, 



1866, p. 361 (catalogue name). — Wachsmuth and Springer, Rev. Palseocri- 



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



