CieverOpisSCus, FALE. 
IN a recent paper in this JourNAL,’ I figured and described 
some peculiar disk-like fossils from the Niagara limestone at 
Joliet, Ill., identifying them with Hall’s genus Cryftodiscus, and 
interpreting them as the possible casts of the gastric cavities of 
Meduse. At the time these descriptions were written a part of 
the material had been in my hands for two years or more. As 
the paper was going to press, too late for revision, additional 
material which suggested an entirely different interpretation, 
came into my hands from the collection of Mr. E. E. Teller, of 
Milwaukee, Wis. These new specimens are from the dolomitic 
Niagara limestone of Racine, Wis., and like the others are casts, 
the actual substance of the fossil being dissolved out. This new 
material shows that the disk-like bodies are not the complete 
fossils, but that they are attached to the summit of a tube com- 
posed of regularly arranged plates. 
The disk portion of the fossil, to which Hall gave the name 
Cryptodiscus, was fully described in my former paper. It consists 
of an expanded disk with a variously lobed periphery, composed 
of four equal plates which occupy the position of the four quad- 
rants of the disk. Figure 1, Plate A, and Fig. 6, Plate B repre- 
sent the impressions of the lower and upper sides of a very com- 
plete specimen from Racine. It is similar to the specimen to 
which the name Cryftodiscus digitatus was given in my former 
paper, but differs from that species in the lobing of the periph- 
ery. If broken off at the bottoms of the lobes it would have 
the contour of C. kydet. The lower side of the disk with its 
central funnel-shaped depression with the central elevation is 
not different from those formerly described, but the upper side 
of the specimen is more nearly perfect than any of those. It is 
™“ On the Presence of Problematic Fossil Medusz in the Niagara Limestone of 
Northern Illinois.”—Jour. GEOL., Vol. V, p. 744. 
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