MEDINANj NIAGARAN, AND CHESTER FOSSILS 
71 
the specimen of Phaenopora expansa Hall and Whitfield, illus- 
trated in 1893/® excepting that one of the specimens has a more 
distinct lobation along one part of its margin. None of the 
specimens are dichotomously branched as in the species of 
Buthotrephis described from the Bertie member of the Cayugan 
in the Buffalo area of New York, or those described from the 
Kokomo member of the Cayugan of northern Indiana. Although 
to the unaided eye these fronds appear flat and continuous, 
under the microscope the frond appears to possess a structure 
consisting in part of longitudinal lines connected by cross lines, 
producing oblong or oval meshes, the whole somewhat resembling 
a Dictyonema. Of the more or less branching longitudinal lines 
there usually are from 7 to 8 in a width of 5 mm. Of the oblong 
or oval meshes there are about 5 or 6 in a length of 5 mm. It 
is impossible to determine from the material in hand how the 
walls of these meshes are constructed. Apparently they are 
built up of fibers, more or less reticulating, so as to produce 
' narrow walls more or less vertical to the plane of the fronds, at 
least along that part of the walls which lies nearest the surface 
of the frond. The inner part of the frond appears to consist 
of a continuous sheet of black material, although it is possible 
that here the fibers are merely more closely interlaced. It is 
impossible to determine whether the oblong or oval meshes occur 
only on one side or on both sides of the frond. If they locate 
anything corresponding to zooecia, it has been impossible to 
verify this fact. 
Locality and formation.^ — ^Associated in the same fragments 
with Leveilleites in the basal members of the Manitoulin dolomite, 
at Credit Forks, Ontario. 
Dictyonema scalariforme creditensis Var. nov. 
Plate IV, fig. B 
Dictyonema scalariforme Foerste, Bull. Sci. Lab. Denison 
Univ., 2, pt. I, 1887, p. 108, pi. 8, figs. 28, 29; Geol. Surv. Ohio, 
Pal. 7, 1893, p. 600, pi. 27, figs. 28, 29. 
Foerste, A. F., Fossils of the Clinton group in Ohio and Indiana: Ohio Geol. 
Surv., vol. 7, pi. 29, 1893. 
