598 THE CEINOIDEA CASIEEATA OF NORTH AMERICA. 



their arrangement is regular, and the plates nodose. Orals cannot be recog- 

 nized. Anus excentric, slightly raised above the general surface of the disk ; 

 the opening directed anteriorly, although occupying the posterior side of the 

 disk. Column composed of rather short joints, the nodals a little the widest ; 

 axial canal moderately small. 



• Horison and LocalUy. — Lower Burlington limestone ; Burlington, Iowa, 

 and Sedalia, Mo. 



Remarlis. — Actinocrinus senarius was described from a specimen of this 

 species in which the last bifurcation in the calyx is broken away, and which 

 was supposed to have but six arms to the ray. 



Physetocrinus Copei (S. A. Millek). 

 Plate LXIU. Fig. 5. 



1881. Actinocrinus Cojiei — S. A. Miller; Joura. Cincin. Soc. Nat. Hist., Vol. IV. (Decbr. number), 



Plate 7, Mgs. 3fl, b, c. 

 1885. Phjseiocrimis Cojiei — W. and Sp. ; EeTision PalsBocr. Part IH., p. 113. 



Nearest to Physetocrinus ornahis, but with fewer and larger plates, and 

 the calyx proportionally higher ; height and width as seven to eight. Sides 

 of the dorsal cup evenly spreading from the foot of the basals to the top of 

 the costals, and thence more rapidly to the arm bases, where the interspaces 

 between the rays are deeply depressed. Ventral disk hemispherical, occupy- 

 ing about one third the height of the entire calyx. Plates of the dorsal cup 

 a little convex, covered with well defined ridges, meeting in the centre of 

 the plates and running to adjoining ones. There are three ridges between 

 the radials and basals, and two from one radial to another, which together 

 form concentric triangles. The ridges between the other plates are single, 

 but within the corners of their triangles there are angular nodes, which are 

 sometimes connected and also form triangles. 



Basals short, their lower margins somewhat projecting outward and 

 crenulated at the edges ; interbasal suture lines slightly grooved. Eadials as 

 long as wide. Costals nearly as wide as the radials, but one third shorter ; 

 the first hexagonal, the second heptagonal. Distichals and palmars smaller 

 in proportion, both angular on the back ; the latter supporting the arms, of 

 which there are four to the ray. Arm facets large. Regular interbrachials : 

 1, 2, 2, 2, vei'y gradually decreasing in size. Anal plate usually a little 

 smaller than the radials ; followed by 2, 3, 3 and 3 plates. Interdistichals 

 one, elongate. Ventral disk plicated around the margin ; the surface of the 



