70 Cincinnati Society of Natural History. — 
this species from P. granulosus, and other species having about the 
same size and general outline. The appearance of having been carved 
out, which is presented by the ambulacral plates, suggested the specific 
name, 
The dorsal side and madreporiform tubercle unknown. 
This species is founded upon a single specimen, from the upper part — 
of the Hudson River Group, near Waynesville, Ohio, and is from the 
collection of I, H. Harris, Esq., of that place. 
CYCLOCYSTGIDES MAGNUS. 
Plate I., fig. 2, natural size; fig. 2a, magnified two diameters. 
Cyclocystoides magnus, Miller and Dyer, 1878, Jour. or Cin. Soc. or Nat. Hist., vol. i., p. 
po. pl. Ti. fics’ 8, Sa. 
The specimen of this species now before me has been worn upon the 
surface, and much of the plates composing the ring has been rubbed 
off, and three of the plates have been entirely removed; but, otherwise, 
étis much better than any I had seen, at the time, of establishing the 
species; indeed, it is the only specimen in this genus, that [ have ever 
seen, from which one could gather any idea of the central part of the 
disc or body. In comparing the original illustration with that now 
given, one must bear in mind, that the inner part of the rim of the 
specimen now illustrated has been worn down to the level of the outer 
rim, and the scars or mammillary elevations are scarcely discernible, 
though enough can be detected to show the double character of the 
plates forming the ring, and to leave no doubt of the correctness of the 
specific identification. 
The ring that surrounds the disc is composed of twenty plates, 
arranged, with reference to their length and connection with the central 
part, into ten pairs. Two of the shorter plates, each having two 
radiating channels toward the central part of the disc, are followed 
by two ofthe longer plates, each of which is possessed of three radiating - 
channels. This arrangement furnishes fifty channels connecting the 
ring with the radiate system of the disc; but the two chan- 
nels from one of the shorter plates, unite with the three channels of the 
adjoining longer plate, before reaching the central part of the disc, 
and, at this part of the disc, the channels are, therefore, reduced to 
ten. The central part of the disc of our specimen is too much in- 
jured for us to follow this system nearer to the center. The injury is 
apparent in fig. 2, but in the magnified view, fig. 2a, the injury is 
patched up by the erroneous substitution of plates. Whether, there- 
fore, the central part of the disc was connected with the ring by ten 
channels, which increased, by bifurcation, as they approached the ring 
