MEDINAN, NIAGARAN, AND CHESTER FOSSILS 
67 
and 7B on plate V, by figures 13, 14, 15, 16, 17, 18A, 19, and 
21A on plate VI, and by figure 25 on plate IV. Additional 
figures of 3 A, 21 A, and 25 are presented on plates VII and IX. 
In specimen 2 the median rachis-like film is 0.4 mm. in width. 
Among the reticulating fibers several series of black dots num- 
ber 6 or 8 in a length of 0.5 mm. Hair-like fibers extending 
beyond the margin of the frond are well shown. 
Specimen 3A shows traces of the median rachis-like film. 
Some of the meshes enclosed by the reticulated fibers are about 
0.2 mm. in dmmeter. Distinct black dots near the median part 
of the frond number 5 in 0.5 mm. Some of the hair-like fibers 
present similar series of dots of smaller size, regarded as denticu- 
lations on the sides of these fibers. The larger dots within the 
flat area of the frond may have served as points of attachment 
of some of the hair-like fibers. 
The frond in the lower right-hand corner of specimen 7 has a 
rachis-like film 0.5 mm. wide. The black dots belonging to the 
reticulating fibers number 5 in 0.5 mm. Those belonging to the 
hair-like fibers number 7 in the same distance. 
In specimen 13 the main rachis-like film is 0.7 mm. wide, the 
corresponding parts of the lateral lobes are 0.4 mm. in width. The 
specimen 14 has a main rachis-like film 0.4 mm. wide, the lateral 
median films being 0.3 mm. in width. The frond apparently 
was about 0.1 mm. thick. Seven black dots occur in a length 
of 0.5 mm. on the. surface of the frond, but these dots are as fine 
as those belonging to the hair-like fibers.' In specimen 15 the 
width of the rachis-like film is 0.5 mm. In specimen 16 its width 
is also about 0.5 mm. The corresponding lateral films are 0.3 
mm. wide. Black dots tend to occur locally in diagonally 
intersecting series. Between 6 and 7 dots occur in a length of 1 
mm., apparently serving as points of attachment for the hair- 
like fibers. In specimen 17 the main rachis-like film is from 0.7 
to 0.8 mm. wide; the corresponding lateral structures are 0.4 
mm. wide. Near the margin of the frond 4 to 5 black dots occur 
in a length of 0.5 mm. 
In specimen 18A the rachis-like film is 0.3 mm. wide. The 
substance of the frond evidently consists of something more than 
