188(5.] NATURAL SCIENCES OF PHILADELPHIA. 215 



STEPHANOCRINUS Conrad. i 



184-2, Conrad, Journ. Acad. Nat. Sci. Phila., vol. 8, p. 278. 



1851. Hall, Palaeoiit. N. York, vol. ii, pp. 212 and 351. 



1851. F. Roemer, Wiegmann's Archiv f. Naturgesch. Jahrg. xvi, vol. i, 



pp. 365-375. 

 1853. Job. Miiller, Verb. d. Berl. Acad. d. Wissenscli., p. 211. 

 1855. Lith. Geogu. (Ausg. 8), p. 266, 

 1857. Pictct, Trait e de Paleoiit., vol. iv, p. 304. 

 1862, Dujardin and Hupe, Hist. Natur, des Zoopli., p. 266. 

 1879. Hall, 28tli Rep. N. York St. Cab. Nat. Hist., p. 146. 

 1881. Hall, lltb Ann. Rep. of Indiana, p. 279. 

 1879. Zittel, Handb. d. Palseont. i, p. 436. 

 1883. Carpenter, Ann. and Mag. Nat. Hist., Apr., p. 237. 



Stephanocrinus resembles in many respects certain forms of the 

 Blastoidea, but has true brachial appendages. The cal3'x is sub- 

 pyramidal, or deeply cup-shaped, with five spiniform interradial 

 processes. 



The basals form a large semicircular or subturbinate cup, more 

 or less truncate at the bottom, with a trigonal distal face, which is 

 slightly excavated for the reception of a column. They consist 

 of three pieces, almost coequal as to size but not as to form, one 

 of them being quadrangular, the two others pentangular. The 

 quadrangular piece takes the position of the smaller basal in the 

 Blastoidea, to the right of the anterior radial ; contrary to other 

 Palaeocrinoidea in which it occupies the left side. In one speci- 

 men, however, exceptionally, it is placed posteriorly, supjjorting 

 the greater half of two postero-lateral radials. 



The first radials are large and resemble to a large extent the 

 forked plates of certain species of Cadaster and Phaenoschisma, 

 in which the limbs the prongs of the fork of two contiguous 

 radials extend up between the arms in an almost vertical direc- 

 tion, but instead of forming, as there, a sort of pyramid, they 

 are extended in Stephanocrinus frequently into long thornlike 

 processes, which sometimes attain more than one-half the height 

 of the calyx up to the arm bases. These processes form radially 

 a deep gutter, containing the ambulacral groove which leads to 

 the arms. 



The second radials rest within a horseshoe-like depression near 

 the outer end of the gutter. The plates are reniform, small, short, 

 axillary, with three conspicuous prong-like projections extending 



