276 F. B. Meck—Descriptions of new Silurian Fossils. 
are wider than long, and increase rather rapidly in size inward 
to the margin of the disk, which is made up of smaller pieces ; 
a few very minute pieces apparently sometimes occur between 
the rows on the dorsal side of the rays. Surface of dorsal 
pieces a little roughened, but apparently without spines. 
Madreporiform piece rather small, a little oval, or almost ar 
cular, nearly flat, and marked by very fine, irregularly inter- 
rupted radiating striz. Ventral side unknown. 
Greatest breadth across, between the extremities of rays on 
opposite sides, 0°90 inch; length of rays, 0°35 inch ; breadth of 
same at inner ends, about 0°22 inch; length of madreporiform 
pieces, 0°08 inch; breadth of same, 0-07 inch. 
This species seems to be related to P. matutinus Hall, but 
want the well-defined madreporiform pieces seem in the species 
The only specimen of this species I have seen is firmly 
attached to a foliated expansion of coral, so as to conceal the 
ventral side entirely. It was evidently lying dead on its back, 
on the bottom of the sea, when the coral commenced growin 
. 
upon its ventral side; and afterward the coral not only covere 
ties of its rays. 
Locality and position—Cincinnati group of the Lower 
Silurian, at Cincinnati, Ohio. Mr. Dyer’s collection. os 
Note.—A fine star-fish recently sent to me by Mr. Dyer, from 
the Cincinnati rocks, presents many features indicating close rela- 
