58 
AUG. F. FOERSTE 
any of the Pleurotomariidae. It does not possess the conical 
spire of Euconia. Externally it resembles such forms as Stra- 
parollus hippolyta Billings, and Straparollus mopsus Hall, but 
its umbilicus is much smaller. While the relationship of this 
species to Straparollus must remain in doubt, in the absence of 
any knowledge of the surface features, it is not out of place to 
refer to the absence of definite knowledge of any structure in- 
dicating affinities with the Pleurotomariidae. 
C. FOSSILS FROM THE BASE OF THE MANITOULIN LIMESTONE AT 
CREDIT FORKS, ONTARIO 
For many years it has been customary to refer certain flat 
branching structures found in Ordovician and Silurian strata to 
the algae. Some of these, in more recent years, have been re- 
garded as due to worm borings, worm tracks, and even to the 
cutting action of flowing water. Those, however, which con- 
sist of thin black films can not be passed over so lightly, and must 
be regarded as at least of organic origin. 
The black coloring of the latter specimens usually is regarded 
as due to plant origin, being derived in a manner analogous to 
the derivation of coal from plant material. 
Usually this black material, in the plant-like organisms found 
in Ordovician and Silurian strata, does not present any structure. 
In the summer of 1911, however, the writer found numerous 
fragments of plant-like fronds in one of the quarries at Credit 
Forks, in southern Ontario, Canada, which under the microscope 
presented distinct, though limited evidence of structure. During 
the geological congress held in the summer of 1913 the writer 
served as guide to a small party of geologists, and on this occasion 
Chris Andrew Hartnagel of the Geological Survey of New York 
and Dr. E. 0. Ulrich of the United States Geological Survey 
found the remarkable specimen here described as the type of 
the genus Leveilleites. 
At first these frondose specimens were regarded as belonging 
to the algae, and an attempt was made to find algal forms with 
corresponding outlines. The reticulating fibers forming the 
body of the fronds were interpreted as corresponding to the 
