628 THE CRINOIDEA CAilERATA OF NORTH AMERICA. 



ton, and, with the exception of the aberrant and doubtful C. glans, did not 

 survive it. Teleiocrinus 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 Hall. 

 Plate LIX. Fig. 7, and Plate LX., Figs. 2a-d. 



1858. Actinocrinus umbrosus — Hall; Geol. Rep. Iowa, Vol. I., Part II., p. 590, Plate 11, Figs. 3«, b. 

 1866. Slrotocrimis umbrosus — Meek and Worthen; Geol. Rep. Illinois, Vol. II., p. 190; and ibid., 



Vol. V„ p. 300, Plate 8, Kg. 5. 

 1881. Teleionrimts umbrosus — W. and Sp. ; Revision Palseocr., Part II., p. 149. 

 1889. Teleiocrinus umbrosus — S. A. MiLLEu; N. A, Geol. and Palaont., p. 286. 



Syn. Actinocrinus regilops Hall; 1860, Suppl. Geol. Rep. Iowa, p. 5. 



Sjn. Strotocrinus le.gilops — Meek and Wobthen; Geol. Rep. Illinois, Vol. 11., p. 190. 



Syn. Teleiocrinus tpgitops — W. and Sp.; Revision Palicocr., Part IT., p. 148. 



Syn. Teleiocrinus agilops — Whitfield; 1893, Mem. Am. Mus. Nat. Hist. N. T., p. 21, Plate 2, 

 Pigs. 27, 28. 



Syn. Actinocrinus ielicaius M. and W. ; Geol. Rep. Illiaois, Vol. V., p. 343, Plate 8, Pig. 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 doi'sal 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 



