ACTINOCRINID.2. . 569 
generally but one between.the other plates; none, however, above the sec- 
ond costals and second interbrachials. The ridges passing up the costals are 
most prominent, and the plates themselves longitudinally angular, their sides 
being almost even with the flattened interbrachial areas, which gives to this 
part of the calyx a peculiarly angular aspect. 
Basals large, forming a deep cup expanding at both ends, the plates hav-. 
ing a projecting rim or transverse ridges around their lower margins, which, 
being truncated toward the sutures, give to the lower face of the cup a tri- 
lobate outline. Radials large in proportion to the plates above. First cos- 
tals less than half the size of the radials ; the second one third shorter than 
the first, and directed obliquely outward. Distichals all axillary, quite small, 
angular on the exterior, their lateral ends bending inward. They support an 
arm at one side, and three palmars at the other, above which there are four 
more bifurcations, all taking place from the third plate respectively, giving 
off an arm to one side, which alternates with the arm of the preceding order, 
except the upper series, which supports two arms. The main arms, as well 
as their lateral branches, are quite delicate, the former uniserial to the fifth 
bifurcation, the latter biserial from their origin. Regular interbrachials: 1, 
2, 4, followed by a few smaller plates, which are on a level with the arm 
bases, and rest against the orals. Anal plate considerably smaller than the 
radials, and supporting two plates in the first row, three in the second, and 
five or six in the third. Interdistichals unrepresented. Tegmen depressed- 
convex, with a strong anal tube rising abruptly from the summit; the plates 
tuberculous. Orals larger than the interambulacrals, and separated from 
each other by the ambulacral plates, which are large, and pass out between 
them in two well defined alternate series, diminishing toward the arms, and 
branching outward. Column of moderate size; the-nodal joints somewhat 
thickest, and rounded upon the edges. 
fforizon and Locahty.—- Upper part of Upper Burlington limestone ; 
Burlington, Lowa, and Pleasant Grove, Iowa. 
Types in the collection of Wachsmuth and Springer. 
Ltemarks. — This species in its arm structure approaches the genus Ste- 
ganocrinus, and is also interesting for its regularly arranged, large covering 
pieces, which pass out between the ambulacra. It is named in honor of Dr. 
Horace G. Griffith, of Burlington, who, with a liberality for which we have 
been often indebted to him, presented us one of the type specimens. 
72 
