ACTINOCEINID^. 577 



large and axillary. Of the palmars only one plate is preserved, and so the 

 number of arms cannot be accurately ascertained from the specimen ; but to 

 judge from the size of the arm openings, it is quite probable that it had an 

 additional bifurcation, and the species had sis arms to the ray, but not eiuht 

 as suggested by MiUer. Arm facets directed horizontally. Eegular inter- 

 brachials : 1, 2, 2 ; the first very large, rising to the top of the second cos- 

 tals ; those of the third range meeting the interambulacrals. Anal plate 

 smaller than the radials, followed by 2, 2, and 2 plates. Ventral disk con- 

 vex, composed of bnt few plates. The ambulacrals, which are represented 

 by three large pieces over each ray, are spinous ; while the orals are almost 

 flat. Anal tube stout at the base, but rapidly increasing in size upwards. 



Horizon and Locality. — Chouteau limestone ; near Sedalia, Pettis Co., Mo. 



Type in the collection of S. A. Miller. 



Actinocrinus arrosus (S. A. Millee). 

 Flate L V. Figs. 7, and 8a, I, c. 



1892. Blairocrimis arrosus — S. A- Miller; Adv. Sheets ISlli Rep. Geol. Suit. Indiana, p. 41, Plate 7, 

 Figs. 1 to 5. 

 Syn. Blairocrimis bidlatus S. A. Millek ; ibid., p. 41, Plate 7, Pigs- 6 and 7. 



Of medium size. Calyx distinctly quinquelobate, its height equal to three 

 fourths its width in well preserved specimens. Dorsal cup saucer-shaped, its 

 height less than half that of the ventral disk ; the surface deeply sculptured ; 

 the radial plates being strongly keel-shaped, the interradial ones provided 

 with a sharp central node, lea^dng deep, pit-like depressions between the 

 nodes and the ridges. Suture lines indistinct. 



Basal cup small, projecting but little beyond the column, and only the 

 angles of the plates bending upwards ; it is notched at the sutures, and tri- 

 lobate in outline. Radials a little wider than long, covered with a transverse 

 node. Costals as wide as the radials, but only half as long ; the first quad- 

 rangular ; the second pentangular and generally a little larger than the first. 

 Distichals one, small, axillary, supporting apparently a single palmar. Arm 

 openings twenty, arranged in pairs, and directed horizontally or shghtly 

 downward. The number of arms unknown. Interradial spaces subovate, 

 composed at the regular sides of three plates, of which the two upper are 

 quite small, and placed level with the arm openings. The anal plate as 

 large as the radials, and similarly sculptured ; it supports two plates in the 



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