BULLETIN OF THE MUSEUM OF COMPARATIVE ZOOLOGY. 283 
Additional Remarks upon a Fern in the same Slab with Platephemera. 
Some doubt has been expressed as to the age of those insects by Dr. 
Geinitz (Sitz. ber. Isis, 1866, p. 22), who considered them as probably 
belonging to the Carboniferous formation from the fact that Platephemera 
is on the same slab with a fern characteristic of that formation, Cyatheites 
(Pecopteris) plumosa, Mr, Scudder (Geol. Mag., Vol. V. p. 174) says : 
* If, however, Dr. Geinitz’s determination of this species were certainly 
correct, it would not invalidato the statements of geologists, who refer 
this deposit to Devonian, for several species of plants are stated to be 
common to this formation and to the Carboniferous." 
This may be : nevertheless an important gap is still here to be filled. 
Mr. Scudder does not mention the occurrence of this plant together with 
Platephemera, nor is that done in the geological note (p. 40) by Prof. 
Dawson. Among the plants belonging to bed No. 7, no species of Pe- 
copteris or Cyatheites is enumerated by Prof. Dawson. I cannot in the 
Canadian literature at my command find this fern quoted as occurring in 
the Devonian formation. 
I applied to a prominent authority, Mr. Leo Lesquereux, for informa- 
tion, and had the following answer: “ Pecopteris (Cyatheites) plumosa is 
a common species of our middle Carboniferous, found in the strata im- 
mediately above the millstone grit. As yet it has not been found in the 
subconglomerato, still less in the Devonian of the United States, which is 
separated from the conglomerate by the subcarboniferous or the Mauch 
Chunk red shale, very thick formations. "This species is even described 
by White and Fontaine from the Permo-carboniferous. Some of Prof. 
Dawson's species from the Devonian in Canada are found in the true Car- 
boniferous of the United States. We have no positive means of ascertain- 
ing the geological relation, as tho identity of some of Prof. Dawson's species 
is as yet uncertain. This is about all I can say on the subject. For com- 
mon species like P. plumosa, which is the equivalent of P. dentata, the 
geological distribution is generally well marked between the European 
and North American series. We have, however, some types, which are 
found here in the lower Carboniferous, even in the subconglomerate, 
while in Europe they have not been found until now at a lower stage 
than the Permian and the Trias. This difference, however, cannot 
