998 THE CRINOIDEA CAMERATA 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. 
Horizon and Locahty. — Lower Burlington limestone; Burlington, Iowa, 
and Sedalia, Mo. 
Remarks. — 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 (8. A. Mitier). 
Plate LXILL. Fig. 5. 
1881. <Actinocrinus Copec—S. A. Mittnr; Journ. Cincin. Soc. Nat. Hist., Vol. IV. (Dechbr. number), 
Plate 7, Figs. 2a, 6, ce. 
1885. ER Cae and Sp.; Revision Paleocr. Part IIT., p. 113. 
Nearest to Physetocrinus ornatus, 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 pa vatints outward and 
crenulated at the edges; interbasal suture lines slightly grooved. Radials 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, very 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 
