874 FLORAL ZONES OF THE POTTSVILLE FORMATION". 



broad, obtuse, or rounded teeth on the sides of the limb. When 

 further developed this sublobation, which may be seen in specimens 

 from nearly every part of the frond, becomes conspicuous, givino^ the 

 pinnule in its pinnatitid stau"e a Sphenopteroid or Eremopteroid phase. 



Probably the only species of the genus in our Hora with which 

 Mariopteris eremopteroides is liable to be confused is M. pottsvillea. 

 But althou.o-h there is a resemblance in portions of the fronds of the 

 two species, sometimes appearing close on a casual glance, it is randy 

 difficult to distinguish the two forms, even in small fragments bearing 

 simple piiuudes. from the upper part of the pemdtimate pinna'. The 

 pinnules of J/, erciiujpteroidv-s are not so constricted at the base, not so 

 triangular or dilated just above the point of attachment, and, as may 

 almost invariably be noted, they are more or less distinctly lobate or 

 sublobate. even in a younger stage, in which they are still attached ])y 

 the whole base or even slightly connate. In general, the short pinnae 

 of the latter species are more dilated toward the })ase, both the piniiiv 

 and the pinnules being usually smaller, the latter being more frequently 

 connate, as well as lobate and alate. Ver}^ often, too, the pinnules 

 are set out from the rachis by a slight elongation of the basal portion 

 or attachment so as to suggest a very short, broad pedicel, sometimes 

 nearly equaling the pinnule in width. The nervation of M. pottsvillea 

 is somewhat coarser and noticeal)ly more distant and ari-hed. 



The species is abundant at all mines in the horizon of the roof shales 

 of Lykens coal No. 5. Possibly it is present also in the roof of Lykens 

 coal No. (\. 



MaRIOITKKIS I'OTTSVILLEA Sp. UOV. 



PI. CXC, Figs. 3, 3a, 4, 4a, 5, 6. 



Fronds (juadri- or poly- {() pinnate, robust, not very dense; penulti- 

 mate pinna,' alternate, open, the lower at a right angle to the rachis, 

 the upper slightly obliciue. rathiM* distant, lanceolate, or linear-lanceo- 

 late, slightly contracted at the base; rachis somewhat flexuose, 

 coarsely lineate in the major divisions, more finely and irregularly 

 lineate in the smaller divisions, while in the penultimate and ultimate 

 pinna' they are slender, slighth' ilexuose-geniculate, ventrally sulcate, 

 dorsally round, and broadened by narrow decurrent wings of the lamina; 

 ultimate j/nuiie alternate oi- subopposite, open at a right angle or 

 slightly oblic^ue, distant, usually one-half their Avidth or moi-e apart, 

 lanceolate or linear-lanceolate, clearly constricted at tiie base, with a 

 nai'row decui'iing border. 



Piniudes alternate or siihalternate. usually distant, ()l)li<}ue. broadly 

 ovate, or ovate-triangular, asynunetrical, obtuse, or obtusely rounded, 

 venti'ally arched, distinctly constricted at the broad base, which is 

 marked in all the well-developed examples by an inferior rounded 

 sinus, the uppermost pinnules becoming confluent, more olilique and 



