128 FOSSIL CRINOIDS. 



known referable to the genus. Meek and Worthen's reference to it of Roemer's 

 Poteriocrinus pisiformis, from the Sikirian of Tennessee, was erroneous, as that 

 species belongs to the Flexible genus Lecanocrinus ; while Cyathocrinus granu- 

 latus, referred to it by Wachsmuth and Springer, is a Gissocrinus. The statement 

 in the original generic description that there is a lateral anal tube, supported 

 by an anal plate, must fall, in view of what is now known. 

 Revised Generic Diagnosis. 



Calyx small, compared with the relatively heavy arms. Infrabasals un- 

 divided. Anus directly through the dorsal cup, below level of arm bases. 

 Radial facets horseshoe-shaped, deep, concave, occupying only part of width 

 of plate, usually directed outward; perforated by dorsal canal passing into the 

 arms. Arms uniserial, branching frequently, with a fairly regular dichotomy. 

 Pinnules absent. Column round. 



Genotype. Arachnocrinus bulbosus (Hall). 



Distribution. Middle Devonian. America. 



Arachnocrinus bulbosus (Hall). 

 Plate II, figs. 3-12. 



I860. Cyathocrinus bulbosus Hall. 15th Rep. N. Y. St. Cab., 123, PI. I, figs. 19-22. 

 1866. Arachnocrinus buibosus Meek and Worthen, Geol. Surv. 111. II, 177. 

 1879. Wachsmuth and Springer, Rev. Pal., I, 93. 



Type of the genus. A rather small species, with small, globose calyx and 

 ponderous arms; distinguished at once by the great size of its axillary brachials, 

 which are several times as large as the others, extending throughout the rays, 

 giving them a very unusual appearance; average ordinary brachials measure 

 1 mm. high by 3 wide, while the axillaries next to them are 3 mm. by 4.5. Artic- 

 ulating facet on radials facing obliquely outward. Arms long, cylindrical, 

 with frequent bifurcations, and very little taper to the fourth bifurcation, 

 the farthest preserved. Primibrachs very irregular in number, from 3 to 12; 

 shown by five specimens as follows : — 



1. ant. 1. post. r. post. r. ant. ant. 



— 9 7+ 6 — 



— 3 3 3 — 

 5 7+ 5 10 12 

 8 3 4 — — 



— 15 5 3 12-1- 



