GENERAL VERTICAL RANGE OF THE FLORA. 283 



Several biologic features will at once appear from a casual review of 

 the species discussed in the preceding portion of this report. One of these 

 is the great preponderance and considerable diversity of the ferns. These 

 are especially characterized by the presence of a large number of species 

 of Splienopteris and Peco-pteris, mwnj of them representing types generally 

 found at no little distance above the base of the Lower ProductiA-e Coal 

 Measures, or No. XIII of the system of denomination employed in the later 

 State geologic reports of Pennsylvania. In fact, the aggregate of species 

 is distinctly such as is only to be found in the Coal Measures proper. With 

 the exceptions of a very obscure fragment, doubtfully refera,ble to Sphenopteris 

 Hoeninghausii Brongn., and a sohtary specimenh-epresenting a new species 

 of small Mariopteris usually confined to the Sewanee group (Upper Potts- 

 ville), there does not appear to be a species in the collections before me that 

 is not at least varietalh^ different from any I have yet seen in the rich floras 

 gathered from the Pottsville series in the Appalachian province. Even the 

 exceptions just noted are represented by not more than three fragments in all. 



A large proportion of the species in our flora appear to range through 

 a considerable thickness of the Mesocarboniferous in America, and offer 

 us, accordingly, but little correlative aid, except, in some cases, by refer- 

 ence to their first ascertained appearance. Others, like Spiropteris, Hysterites 

 Cordaitis, Conosticlms, Cmilopterisf acantophora, and Excipulites GaUipteridis 

 are presumably little adapted for stratigraphic use on account of their nature 

 and mode of occurrence, though the last named has not, I beheve, been found 

 on any other host than Pseudopecopteris squamosa (Sphenopteris neuropteroides). 

 As representing the former category, or as species insufficiently defined in 

 general, or species whose distribution has not yet been properly studied in the 

 American collections, we may exclude from further consideration Sphenopteris 

 pinnatifida, Pecopteris dentata, the ApJdehice, Callipteridium SulUvantii, Neurop- 

 teris rarinervis, N. Scheuchseri, the Calamites, Asteropliyllites equisetiformis, 

 the AnmdaricB, Sphenophylhmi cimeifoliuvi, S. majus, Sigillaria tessellata, Stig- 

 maria verrucosa, Cordaites diversifolius, and Rliabdocarpos midtistriahis. 



Before dismissing these, however, I should add that a close inspection 

 of many of the species of wide vertical range shows some ver}' interesting 

 chronologic modifications or phases, which, though they may be local, appear 



' CalUpteridimn Owenii enumerated by Lesqnereus in the list of species from Henry County, 

 Missouri, should perhaps also be included, although I have not seen the specimens or specimen on 

 which the record is based. 



