76 TRANS. OF THE ACAD. OF SCIENCE. 
edges of the hexagonal pieces are slightly rounded; the heptago- 
nal pieces obtusely angulated. The radials are hexagonal, 
and about one-third the size of the Ist radials. The 3d radials 
are small, short, heptagonal, and, being axillary pieces, support 
two brachials which are short and hexagonal, 
The interradial pieces amonnt to three between each of the ra- 
dial rows. The first is hexagonal, and its size about the same as 
the 2d radial pieces. It supports two smaller pieces, also appa- 
rently hexagonal. 
Anal pieces.—The first is large, hexagonal, a little elongated, 
and reposes upon the base. This supports on its upper 
two small hexagonal pieces, one of which is larger than the other. 
The form of the succeeding anal pieces can not be determined. 
The vault, compared with the calyx, is very low. It is convex, 
and composed of a number of polygonal plates, often marked with 
smali tubercles, or short ridges. 
€ proboscis is elongated, situated nearest the anal side, and 
tapers gradually as it leaves the vault. A fragment, about a third 
of an inch in length, is all that is preserved in the specimen. 
commencement of the arms is exhibited. 
transverse diameter at base of free arms, about 10 lines; length 
of calyx below arms, 63 lines; height of base, 13 lines; diameter 
of same, 5 lines, ce 
This species is nearly related to Actinocrinus concinnus (nobis), 
but may be distinguished by its smaller size, the greater height of - 
the , and its more elongated calyx. 
_ Locality and formation.—I found this handsome species of Ac- 
tinocrinus near the base of the Archimedes Limestone (Mountam 
pieetons), in the quarries of the Mississippi bluffs, at Quincy, 
ted. : . a 
The ca yx is short, a conical, and occupies about ones 
e base is very iow, wider beneath than above, and its i € 
nal cavity quite shallow. The inferior border is emarginate at 
the sutures, which divide it into three well-defined, broad lobes 
