PLATYCRINIDAE 
57 
Marsipocrinus rosaeformis (Troost) 
Plate IS, figs. 1-8; ig, figs, g, ga 
Cupellaecrinites rosaeformis Troost, Am.. Jour. Sci., 1849, p. 419; Proc. Am. Assn. Adv. Sci., 1850, p. 61 
(nom. nud.). — Cupellaecrinus rosaeformis Shumard, Trans. Acad. Sci. St. Louis, 2, 1866, p. 361.-^ 
Marsipocrinus rosaeformis (Troost) Wood, Bull. 64, U. S. Nat. Mus., 1909, p. 37, pi. 13, figs. 5, 6. 
A large species, typical specimens 12 mm. height of calyx by 30 mm. width, 
to a maximum of 15 by 40 mm. Calj^x concavo-convex or hemispheric; if rest- 
ing on a plane surface will touch by radials or arm-bases. Basal pentagon flat, 
relatively small, about one third the total diameter, usually with a small rim 
around the column-facet. RR horizontal, with facets directed out or down- 
ward; axillary IBr very small, triangular, not over one third the width of the 
radial, flanked by large transversely elongate IIBr which rest upon the radial 
and meet by their short inner faces above the axillary; they curve around on 
the outer side, abutting upon the large iBr and the smaller ones above, and are 
followed by higher brachials leading to the biserial arms. iBr large, arched, 
projecting in a curved lip outward and upward, often strongly corrugated or 
wrinkled, giving to the calyx a decagonal outline as seen from above; a much 
smaller plate abreast of the iBr at either side rests upon the IIBr, sometimes 
limited to the tegmen. Arms stout, biserial, two to the ray. Tegmen broadly 
arched, larger than dorsal cup; plates strongly nodose, shading to angular in 
some specimens, somewhat obscuring the ambulacra, which are not conspicuous. 
Surface ornament of cup very strong, either in form of a simple corrugation 
with wrinkles or tubercles not forming lines, or more or less confluent in radiat- 
ing lines forming triangles, or parallel striae. 
Tliis is the most prominent species in the Tennessee collections, represented by many 
fine specimens mostly obtained from the excavations. Comparison of Troost’s type specimen 
in the National Museum, as figured in 1909, although in poor condition, established that the 
hemispheric calyx is the typical form, and enables us to assign to the species the other char- 
acters so fully illustrated by the new material. The specimen figured herein, pi. 15, figs. 9, 
ga, reproduced from my work on ScypJiocrinus, 1917, ph 9, figs. 5, 5a., as M. tennesseensis, 
is probably referable to this species. 
Horizon and locality. Chiefly Encalyptocrinus zone of the Beech River formation, 
Brownsport group, Niagaran; Tuck’s Mill, near Decaturville, Decatur County, Tennessee. 
Marsipocrinus tennesseensis (Roemer) 
Plate 14, figs. 1-6 
Platycrinus tennesseensis Roemer, Sil. Fauna Westl. Tennessee, i860, p. 35, pi. 3, figs. 4a-/. — Platycriniis 
(Cupellaecrinus) tennesseensis Shumard, Trans. Acad. Sci. St. Louis, 1866, p. 362. — Marsupiocrinus 
tennesseensis, Wachsmuth and Springer, Rev. Pal., 2, 1881, p. 65; Proc. Acad. Nat. Sci. Phil., 1888, 
P- 373, pl- 20,. fig. 7 ; N. A. Crin. Cam., 1897, p. 731, pi. 75, figs. i6a, b. — Wood, Bull. 64, U. S. Nat. 
Mus., 1909, p. 31, pl. 9, figs. 5, 6. — Bassler, Bibliogr. Index, 1915, p. 788. 
Similar to M. rosaeformis in size, general proportions and form of iBr 
plate, but with calyx bi-convex, and dorsal cup and arched tegmen about equal. 
