304 The American Geologist. Mayer 
vation and is surrounded by a low narrow rim. All of the 
dorsal plates are more or less convex or low tumid, those of 
the radial series being broader than long. The first radials 
are six and seven sided while the second plates of the series 
are four sided. The third or axillary plates are five sided in the 
right and left posterior rays, but hexagonal and non-bifurcating 
in the other three rays in most of the specimens. 
In one of the rays of a detached dorsal cup the second 
radial plate is an axillary piece. The series of double arm 
pieces rests directly on the third radial plate. The first inter- 
radial plate is a little longer than broad and supports above 
two elongate pieces that fill the depression between the arm 
bases. The first azygous interradial is about as long as broad 
and supports above three somewhat smaller pieces of equal 
length and width, two being seven sided and one six. Above 
these are two series of three smaller plates each, to the top 
of the arm lobes. 
The anterior and the two antero-lateral rays give rise to but 
one arm each (in one specimen, the right antero-lateral ray 
has two arm bases) while the right and left posterior rays 
support two arms each, making seven (eight in one specimen) 
arms in all, the fewest number yet observed on an Agarico- 
crinus. 
The ventral disk is strongly elevated and the plates both 
of the ambulacral and interambulacral areas are more or 
less tumid except those of the anal area which are smooth, 
the area itself being extravagantly elongate and inflated. The 
small anal opening is situated near the top of this inflation 
and the sides and top of this smooth, inflated area are bounded 
by a line of strong nodes somewhat after the manner of Agar- 
icocrinus orontrema but in A. praecursor the anal opening is 
not at the bottom of a pit. The strongest nodes of the ven- 
tral disk are above the arm bases. 
A detached ventral disk of a somewhat larger specimen ap- 
parently of this species has the immediate region about the 
anal opening somewhat flattened and entirely surrounded by 
a ring of nodes, the latter invading the lower part of the anal 
interambulacral area. On this specimen the nodes become 
spine like and flattened processes. 
This interesting crinoid was obtained from the limestone layers 
of the Chontean beds at Fern Glen, St. Louis Co., Mo., and the type 
