87<') FLOKAL ZONES OF THE POTTSVILLE EORMATION. 



Still. Nvhilo there i.s sc-airoh' room for doubt that J/. ;?t'/'r6>6'rt was either 

 derived from J/! inuriatta or a common, slightly earlier stock, the 

 analogies of the vertical distribution of the American species of Mari- 

 optii'ls lead naturally to the expectation that the latter type will be 

 found to occur consideral)ly lower in the stratigraphic series of 

 Europe and to disappinir much earlier than the former, although 

 through a portion of the Coal Measures they may have existed side 

 by side. In the American sections the form designated in this report 

 21. tennesseea7icu which is possibly nearest to the plant figured as 

 PecopteriH niurieata by Brongniart. predominates at the base of the 

 Sewanee group and hardly survives in the normal type to mingle with 

 the small, delicate, thin-nerved variety which appears, in the American 

 Carboniferous, to l)e the earliest representative of 21. nervoi^a., occur- 

 ring in the uppermost portion of the Pottsville series. 



The relations of 2Iar'iopterU miiricata and the type designated in 

 our Amei-ican literature 21. nervom have been specially discussed 

 in my remarks on the forms occurring in the McAlester, Indian Ter- 

 ritory, coal rield.^ 



The characters enumerated above readih' distinguish 2Lai'iopferi8 

 potiHnlha from those European forms known as 2L. murkata and 21. 

 nervosa. The form typically described in the American literature as 

 I^eudopecopteru nerrosa (Brongn.) Lx. has larger, broad, triangular, 

 acute, closer, unconstricted pinnules, with much stronger, more dis- 

 tant, straighter nerves. The species described in manuscript by Dr. 

 Newberry as Ve<-opt<rix inlJata is a much smaller plant, with sessile, 

 close, thin pinnules and finer nervation. Einally, J/, tennesseeana is 

 a more robust fern, with compact, close pinnules or lobes, the upper 

 ones confluent, very o])li(|ue. and not so contracted at the base. 



This species is common at all localities in the ht)rizon of the roof 

 shales of Lvkens coal No. 4, and is apparently unknown at any con- 

 siderable distance from that level. 



The plant is found in good examples at the Lincoln mine, the Brook- 

 side mines. W'illiamstown. the upper Eureka drift, and in a shaft 

 about lit It) viirds northc^ast of the north Brookside slo])e. Good S])ring; 

 at the Broad Mountain mines, at Swataia Gap. and in the Pottsville 

 Gaj). 



Mauioi'TKIMs i"^(;>lka sp. nov. 



PI. CXCII, Fig. 2-6. 



Frond small, compact; rachis rtdatively strong, lineate. deeply 

 depressed, ventrally canaliculate; pemdtimate pinna^ilternate. nearly 

 at a right angle to the rachis. close, touching oi' overlapping, lanceolate 

 or linear-lanceolate, acute or acuminate; ultimate pinnte alternate, 



Nineteenth Ann. \W\>\. V. S. Gcol. Snrvey. Pt. HI, i>. 175. 



