638 THE CEINOIDEA CAMEKATA OF NOKTH AMERICA. 



Bemarks. — We cannot place Strotocriims and Teleiocrinus together in the 

 same genus, as was done by Meek and "Worthen, for they evidently have 

 a different origin, the former being developed from Physetocrinus, the latter 

 from Cactocrinus. The modifications that took place in the two forms were 

 in the same direction, and this accounts for the resemblance which unques- 

 tionably exists between them. A very interesting feature of this genus, 

 which has not been observed in Teleiocrinus, is the incorporation of the 

 lower pinnules, the plates of which take the form and office of interbrachial 

 and interdistichal plates. 



Strotocrinus regalis Hall. 

 Plate LXV. Figs, la, h, c, d. 



I860. Adimcrinus regalis — Hall; Suppl. Geol. Rep. Iowa, p. 9. 



1866. Strotocrinus regalis — Meek aud Worthun; Geol. Rep. Illinois, \a\. II., p. 190. 



1873. Strotocrinus perumbrosus — Meek and Wokthen ; Geol. Rep. Illiuois, Vol. V., p. 357, Plate 8, 



Fig. 4. 

 1881. Strotocrinus regalis — W. and Sp. ; ReYision Palteocr., Pai-t 11., p. 160. 



Sjn. Actinocrimis perumbrosus — HiLL; 1860, Snppl. Geol. Rep. Iowa, p. 7- 

 Syn. Actinocrinus speciosus Meek and Worthen ; 1860, Proceed. Acad. Nat. Sci. Pliila,, p. 386. 

 Sja. Strotocrinus bloomfieldensis S. A. Miller ; 1879, Journ. Gincin. Soc. Nat. Hist, Plate 15, 

 Fig. 6. 



An extremely large species, the calyx across the rim to the last bifur- 

 cation reaching sometimes a diameter of 12 cm., and a height from the foot 

 of the basals to the base of the rim of 5| cm., and to the tips of the arms 

 about 15 cm. Dorsal cup urn-shaped, the sides a little convex; the distichals 

 bending abruptly outward, and forming the base of the rim, which slopes 

 a little upward. Tegmen almost flat, often depressed in the middle. Plates 

 of the cup convex, covered with strong, angular ridges, which rarely meet 

 in the centre of the plates, but rim to a place near the centre, where they 

 leave a small central depression or bare spot ; sometimes, however, the 

 middle space is occupied by a small transverse node. The ridges are in 

 parallel sets of from three to six ; there are five to six between the radials 

 and basals, and from two to three between the other plates. The surface of 

 the brachials in the rim is sharply elevated into angular, longitudinal, zigzag 

 ridges, which distinctly mark the lines of bifurcation, and leave between 

 them broad shallow grooves, which are paved at the bottom by the plates of 

 the fixed pinnules. 



Basals very large, forming a deep cup, the sides of the plates beveled. 



