FOSSIL MEDUS4 IN THE NIAGARA LIMESTONE 749 
The specimens figured are from the collection of Mr. L. H. 
Hyde. 
Cryptodiscus digitatus n. sp. Figs. 6-7. 5? 
Only the detached quadrants of this species have been observed. 
Each quadrant is deeply divided into three primary lobes, the 
two lateral lobes being again divided in a manner not clearly 
shown in the specimens. Surface covered with fine pits which 
are coarser towards the proximal angles. Central depression 
narrow and deep. 
In one specimen, Fig. 5, which may belong to a distinct 
species, the central lobe of the quadrant is deeply bifurcate, and 
the lateral lobes are more deeply and more divergently divided 
than in the type. This specimen is also of interest in showing 
two quadrants somewhat separated, but still holding their rela- 
tive position. 
The specimens figured are from the collection of Mr. L. H. 
Hyde. 
Cryptodiscus bilobus n. sp. Fig. 8. 
A single quadrant of this species has been observed, but that 
one is nearly perfect. The distal margin is divergently bilobed, 
with each lobe marked by a well defined, rounded, radiating 
furrow which extends nearly to the proximal angle, dividing the 
plane of the quadrant into three subequal triangular areas. 
Each of these areas is ornamented with fine stria which diverge 
from the margins of the two radiating furrows. The central 
depression of the disk narrow and deep. 
The type specimen is in the collection of Walker Museum. 
EXPEANATION OF PEATE. 
FIGS. 1-2. Cryptodiscus corrugatus. 
1. A complete specimen with the periphery imperfect. 
2. A single quadrant showing some of the narrow lobes of the 
periphery. 
Fics. 3-4. Cryptodiscus hydri. 
3. A complete specimen with the periphery imperfect. 
4. A single detached quadrant. 
