192 CRINOIDS. 



Horizon and localities. — Lower Carboniferous, Upper Bur- 

 lington limestone: Ash Grove ( Greene county). 



Physetocrinus ornatus (Hall). 



Plate xxiv, fig. 7. 



Actinocrinus ornatus Hall, 1858: Geol. Iowa, vol. I, p. 583, pi. x, fig. 12. 

 Actinoc7-inus senarius Hall, 1860 : Geol. Iowa, vol. I, Supp., p. 25. 

 Physetocrinus ornatus Meek & Worthen, 1873 : Geol. Sur. Illinois, vol. V, 



p. 349. 

 Physetocrinus ornatus Keyes, 1890: Am. Naturalist, vol. XXIV, p. 254, 



pi. viii, fig. 5. 



Calyx like in P. ventricosus, but with a more depressed or 

 nearly flat ventral surface. Plates of the dorsal cup not very 

 convex and the ridges more continuous, forming well-defined 

 concentric triangles. 



Horizon and localities Lower Carboniferous, Lower Bur- 

 lington limestone: Hannibal, Louisiana, Sedalia. 



Physetocrinus ventricosus (Hall). 



Actinocrinus ventricosus Hall, 1858: Geol. Iowa, vol. I, p. 595, pi. xi, tigs. 



6a-b. 

 Actinocrinus subventricosus McChesney, 1860: Desc. New Pal. Foss., p, 21. 

 Actinocrinus subventricosus McChesney, 1867: Trans. Chicago Acad. Sci , 



vol. I, p. 1, pi. iv, fig. 6. 

 Physetocrinus ventricosus Meek & Worthen, 1873 : Geol. Sur. Illinois, vol. 



V, p. 349. 



Calyx subglobose; the dorsal cup occupying about two- 

 thirds the entire height. Ventral side very much arched, 

 strongly lobed and folded around the margin : made up of a 

 multitude of small ossicles which are often spinous. Anal 

 opening a simple perforation in the test, and situated near the 

 center of the disk. Free arms long, slender, and more or less 

 angulated along the sides. In all other respects the arrange- 

 ment of the plates is as in Actinocrinus. Surface of each 

 piece in the dorsal cup very convex, and marked sets of three 

 or more ribs running from the center of each plate to the 

 adjoining ossicles, while at the corners of each plate is a small, 

 deep, pit-like depression. 



Horizon and localities. — Lower Carboniferous, Upper 

 Burlington limestone: Hannibal, Sedalia. 



