ECHINODERMA TA—CRINOIDEA . 569 



Jurassic of the Big Horn Mountains and Black Hills and of 

 Colorado, Nebraska, Utah, Idaho, Wyoming and Nevada. 



203. P. (Isocrinus) knighti Springer. Jurassic. 

 Stem smooth pentagonal, with straight sides except near the 



calyx where they are stellate; calyx forming low cone, without 

 downward projection of basals or radials. IB well defined, filling 

 half the diameter of column facet; arms 10-20, of about 90 bra- 

 chials, simple or bifurcating once between i6th and 30th distichals ; 

 syzygies at intervals of 5-10 brachials. 



Shirley beds of Medicine Bow and Red Butte, Wyoming. 



Incert.-e sedes. 

 LXXIX. AspiDOCRiNUS Hall. 

 Broadly circular and concave, depressed hemispherical or shield- 

 shaped, with plain or plicate upper margin. Point of attachment 

 for column distinct. 



Possibly the root of a crinoid, or possibly the base of a crinoid, 

 as depressions sometimes present in the upper margin might indi- 

 cate a second row of 10 or 12 radial and interradial plates. 

 Devonic. 



204. A. scutelliformis Hall. Devonic. 

 Diameter about one and one half inches. (Type of genus.) 

 Helderbergian of New York, etc. (Characteristic of Upper 



New Scotland and Becraft limestones.) 



LXXX. Ancyrocrinus Hall. 



Form bulb-shaped, with lateral processes and a central column. 



Represents the lower end of a crinoidal stem, the lateral appen- 

 dages being a kind of radicular cirri used in anchoring the form 

 which is probably free-floating. It may later become detached, 

 leaving the adult free. Devonic. 



205. A. spinosus Hall. (Fig. 1908.) Devonic. 

 Lower part of bulb broadly rounded ; arms short. 



Onondaga of Falls of the Ohio. 



206. A. bulbosus Hall. Devonic. 

 Differs frotp A. spinosus in its longer and less ventricose basal 



portion, its longer and less diverging arms. The column above the 



