84 
SMITHSONIAN INSTITUTION 
Aside from this combination of general characters, the most striking feature is the in- 
equality of the radials, and the distribution of the processes on radial and anal plates in such 
a way that there is an arrow-head projection between the arm-bases in every interbrachial area. 
Processes analogous to these, of various shapes, are characters of Pisocriniis. 
Mysticocrinus wilsoni Springer 
Plate 26, figs. la-g 
Springer, Amer. Jour. Sci., 46, 1918, p. 666, pi. ii, figs. 1-8. 
Calyx very small, the size of small Pisoerinus , about 2.7 mm. height and 
width of type, with but little height added by the infolding arms; flattened be- 
low, strongly constricted at the arm-bases. IBB forming a shallow saucer, ex- 
ternally concave, the smaller r. post, plate being more than one fifth the area 
of the pentagon. BB strongly convex, bent outward and upward, forming about 
one third the height of the cup ; post. B heptagonal, wider than high, subangular 
below, truncate above; r, post, and r. ant. BB hexagonal, the other two pen- 
tagonal. RA pentagonal, truncate above to meet r. post. R, and beveling the 
lower corner of anal. Anal a: very large, sagittaeform, higher than wide, beveled 
laterally by the RA; apex acuminate, rising almost to the height of first secundi- 
brachs ; offsets of arrow-head resting upon and interlocking; with shoulders of 
post. RR. 
RR unequal and differing in shape; angular processes project nearly as 
high as the anal between the arm-bases from three of the RR, viz., at one 
(outer) side of each posterior and at both sides of the anterior R, while the 
laterals have none; each process has an offset like those of the anal interlocking 
with adjacent RR. Radial facets deeply curved, occupying a median position 
except on the tAvo post RR, in Avhich the single outer processes occupy about 
one-half the distal width of the plate and the facets tOAvard the posterior side 
the remaining half. Ant. R. the largest plate in the cup ; it and the two post. RR 
Aviden upAvards, while the tAvo lateral RR correspondingly diminish in Avidth, 
and by reason of the absence of processes are shorter than the former ; the R. 
post. R is the smallest, although Avith the RA added it is about equal to and 
slightly longer than 1 . post. R. Arms unequal, uniserial, branching once, infold- 
ing and apparently very short; the tAvo post, and probably the ant. arms have 
2 IBr, Avhile the laterals seem to have but one; the axillaries are folloAved by 
series of 3 or more subquadrangular brachials Avhich taper gradually. Anus 
and tegmen unknoAvn. Stem circular. 
Horizon and locality. Laurel limestone, at top of chert; St. Paul, Indiana. 
