———e 
628 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
ton, and, with the exception of the aberrant and doubtful C. glans, did not 
survive it. Zeleiocrinus is represented in the lower beds by a single transi- 
tion form, but became established in the Upper Burlington to the extent of 
five species. The phylogenetic development is apparent: The arms of this 
group became so numerous and crowded that they were naturally pushed 
outward for want of room, and their bases, being in such close contact as to 
be immovable, became united by suture, and thus formed the rim. Other 
modifications took place simultaneously at the inner floor of the disk, where 
tubular passages were formed for the reception of the ambulacra; and the 
column, which in this group is comparatively small, was strengthened by 
longitudinal braces. 
Teleiocrinus umbrosus Hatt. 
Plate LIX. Fig. 7, and Plate LX., Figs. 2a-d. 
1858.  Actinocrinus umbrosus — Haut; Geol. Rep. Iowa, Vol. I., Part IL, p. 590, Plate 11, Figs. 8a, d. 
1866. Strotocrinus umbrosus —Munx and Wortusen; Geol. Rep. Illinois, Vol. IL, p. 190; and ibid., 
Vol. V., p. 360, Plate 8, Fig. 5. 
1881. Teleiocrinus umbrosus —W. and Sv.; Revision Paleocr., Part IT., p. 149. 
1889. Teleiocrinus umbrosus —S. A. MittER; N. A. Geol. and Paleont., p. 286. 
Syn. Actinocrinus egilops HatL; 1860, Suppl. Geol. Rep. Iowa, p. 5. 
Syn. Strotocrinus egilops — Muxrx and Wortuen; Geol. Rep. Illinois, Vol. II., p. 190. 
Syn. Teleiocrinus egilops —W. and Spr.; Revision Paleocr., Part II., p. 148. 
Syn. Teleiocrinus egilops — WHITFIELD; 1893, Mem. Am. Mus. Nat. Hist. N. Y., p. 21, Plate 2, | 
Figs. 27, 28. 
Syn. Actinocrinus delicatus M. and W.; Geol. Rep. Illinois, Vol. V., p. 348, Plate 8, Fig. 2. 
A moderately large species. Calyx about as high as its width at the arm 
bases. Dorsal cup conical to the base of the rim, which rises from above 
the distichals. Ventral disk dome-shaped ; its height equal to one third — or 
less — the height of the dorsal cup. Rim wide, almost horizontal. Plates 
exceedingly variable; in some specimens extremely knobby, with corrugated 
or uneven surfaces, in others merely convex and almost smooth; but most 
generally there are short ridges traversing the sutures, which enter the 
margins of the plates, and the middle part is nodose. The nodes of the 
radials are large and massive, and like those of the costals transversely 
elongate, while those of the interbrachials are round and conical. The plates 
of the rim are ridged longitudinally, and in the specimen look like crowded 
free arms. 
Basals thick, strong, their lower margins extended: outward in a thick- 
ened rim, and downward in form of nodes, two to each plate, which project 
ee ————— 
wt 
ht 
; 
ee 
