236 Systematic Paleontology 



6 mm. in width, averaging 1.3 cm. in length by 2.5 mm. in width. 

 Distad the pinnules are united for more than half their length, proximad 

 they are more or less decurrent. There are great irregularities in the 

 latter feature. One secondary limb may be alate for almost half its 

 length, while the other may be pectinate entirely to the base. If it be 

 granted that these forms are comparable with the niodem species of 

 Gleichenia or Dicranopteris, then they show similar irregularities in the 

 suppression and development of the primary axes. Soral characters 

 unknown. 



This species is exceedingly abundant at certain localities within the 

 Patapsco formation of the Potomac valley, to which it is thus far con- 

 fined. Specimens of any size are perfectly characteristic, but small 

 fragments may be readily mistaken for Cladophlehis, Laccopteris, and 

 other genera. The varying appearance assumed by this species is well 

 shown on the accompanying plates. From the abundance of the remains 

 at certain outcrops this species must have been gregarious after the 

 manner of the modem Matonia pectinaia, Dicranopteris fulva, or the 

 various other species of the latter genus, as well as those of the allied 

 genus Gleichenia. The alate rachises suggest somewhat the modern 

 Matonia sarmentosa Baker. (Phanerosorus Copeland, Philip. Journ. Sci., 

 vol. iii, 1908, p. 344.) The writer has seen a specimen of the common 

 Dicranopteris fulva (Desv.) Underwood, collected by Mr. W. R. Maxon 

 in Jamaica, which departs widely from the usual form in the direction 

 of Matonia sarmentosa Baker, and also in the direction of Gleichenia 

 (sens stricto, i. e., with short, rounded segments), which also serves to 

 accentuate the relationship between these various forms, since it is con- 

 ceivable that the alate rachises of Knowltonella Maxoni are near the orig- 

 inal type (or are morphologically short pinnules which have become 

 fused), and the normal pinnules are acquired just as the form of 

 Dicranopteris fulva may be considered as of phlogenetic significance and 

 the normal form the acquired form. Similarly the form of Matonia 

 sarmentosa, while due to the specialized habitat of the species, and in 

 that sense acquired, harks back to the ancestral forms whose pinnule 

 characters antedated those of Matonia pectinata. " 



