BULLETIN OF THE MUSEUM OF COMPAliATlVE 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. 

 Goinitz (Sitz. ber. Isis, 186G, 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, C'l/atheites 

 (^Feco2)teris) pluviosa. Mr. Scudder (Geol. Mag., Vol. V. p. 17-4) says: 

 " If, however, Dr. Geinitz's determination of this species were certainly 

 correct, it would not invalidate 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) pAumosa 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 

 subconglomerate, 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 fi'om the Pcrmo-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 the 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. Jentata, 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 difibrcnce, however, cannot 



