No. 2.] DAWSON — FERN WITH PLATEPHEMERA. 103 



P. phnnosa ; and though he insinuates a doubt as to the validity 

 of some of my Devonian species, even this does not apply, since 

 the species in question was carefully described by the late Prof. 

 Hartt, and accepted by me after study of his material, which 

 included several very considerable portions of well preserved 

 fronds. 



Though doubts and suspicions thus cast on work carefully and 

 exhaustively done, in so far as material exists, should not seri- 

 ously affect the minds of naturalists, I have thought it desirable 

 to set the matter at rest, as far as possible ; and have therefore, 

 through the kindness of Dr. Scudder and the Curator of the 

 Boston Society of Natural History, obtained access to the origi- 

 nal specimen, and would now state the actual facts. 



The fern on the specimen in question (No. 849G of the Boston 

 Society's collection) is undoubtedly Pecopteris serrulata of Hartt, 

 and exhibits in a tolerable state of preservation six secondary 

 pinnae of one side of a primary pinna of the species. To a hasty 

 observer, supposing the specimen to be a piece of Carboniferous 

 shale, it would be natural to refer the fern to P. plumosa of 

 Brongniart or to Aspidites silesiacus of Goeppert, which it per- 

 haps more closely resembles; and since its fructification is still 

 unknown, it may quite as likely belong to the group or sub-genus 

 Aspidites in which Goeppert and Schimper place P. silesiaca, as 

 to that of Ci/(fthites in which Schimper places P. plumosn. 



The distinctive characters indicated by Hartt are principally 

 the form and insertion of the pinnge, the slender crenuiate revo- 

 lute, lanceolate pinnules, and the simple veinlets. Perhaps the 

 most obvious characteristic is the peculiarly elongated acuminate 

 points of the primary and secondary pinnae, in which this species 

 seems to differ from all its near allies. In the specimen in ques- 

 tion, though only a portion of one side of a primary pinna is 

 seen, and its characteristic elongate termination is absent, yet 

 one of the secondary pinnae shows this character very well, and 

 the simple veins and crenate revolute margins may be made out 

 with a lens in a good light. I do not think that any palaeobo- 

 tanist, in view of these characters, would decide to identify this 

 fern with P. plumosa, unless indeed he were of opinion that the 

 whole group to which that species belongs should constitute one 

 broad specific type extending from the Devonian to the Permian, 

 a view to which I should have no objection, provided sufiicient 

 connectina- links can be found. 



