ECHINODERMATA—CRINOIDEA. 



499 



11. Stephanocrinus Conrad. 

 Calyx composed of three elongate B of dissimilar outline, five 

 R and five IR. R deeply forked, the prongs (limbs) formed by 

 the margins of two contiguous R extending upward between the 

 arms and building together with the IR a row of pyramids. The 

 radial cuts are occupied by the ambulacral grooves which are 



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Fig. 1808. Stephanocrinus angulaius, two 

 individuals and enlargement of stem. (After 

 Hall. ) 



Fig. 1809, Stephanocrinus angu- 

 latus, analysis of calyx. (After Hall. ) 



roofed over by two rows of covering pieces. Tegmen composed 

 of five large, triangular orals. Arms very short, composed of 

 about ten pieces, all of which are axillary and give off side arms ; 

 these side arms are biserial, nonpinnulate, and are made up of 

 long, strongly wedge-shaped joints. Stem consisting of circular 

 joints, pierced by a circular canal. Ordovicic-Siluric. 

 3. S. angulatus Conrad. (Figs. 1808, 1809.) Siluric. 



Calyx reverse-pyramidal. Sutures scarcely visible. R 6-sided, 

 with short, forked upper side. IR broad below, contracting to a 

 point above. Strong and angular keels present on the plates. 

 Stem joints thick and equal. 



Niagara shale of New York. 



III. Haplocrinus Steininger. 

 Calyx small, pear-shaped to globose. B 5 ; R 5, unequal. Three 

 of the R composed of two pieces of which the uppermost or su- 

 perradial is the larger and bears an articular facet for the attach- 

 ment of the arms. Arms small, simple, uniserial, resting within 

 deep grooves formed along the sides of the orals. Orals large, 

 five-sided and in contact laterally, the posterior one pierced by a 



