Maryland Geological Survey 239 



Occurrence. — Arundel Formation. Arlington, Maryland. Patapsco 

 Formation. Mt. Vernon, White House Bluff, Virginia. 

 Collection. — U. S. National Museum. 



Family POLYPODIACEAE 



Genus CLADOPHLEBIS Brongniart 

 [Tableau, 1849, p. 25] 



This genus is essentially a form-genus which is restricted at the present 

 time to include only certain fern remains of Mesozoic age, although this 

 type of frond is practically identical with those of some Paleozoic genera, 

 as, for example, Pecopteris, and it can also be closely matched by a va- 

 riety of Tertiary and living ferns. 



Cladophlehis was proposed by Brongniart in 1849 for those species 

 which formed the section Pecopteris neuropteroides in his " Histoire des 

 vegetaux fossiles," which he regarded as transitional between Pecopteris 

 and Neuropteris. Certain of their characters were mentioned but no 

 formal diagnosis was attempted. Saporta, who was perhaps the first 

 to define the genus with precision gives the following characterization: 



" Frons pinnatim divisa, pinnulge ab alterutra discretse vel vix inter 

 se cohserentes rachi tota basi adnatse aut plus minusve contractge subque 

 auriculataB integrge rariusve dentatse; nervuli e nervo medio orti apicem 

 versus attenuati vel evanidi primum obliqui, dein curvati furcatoque 

 divisi.^' ' 



Sehimper, in 1874, gives a somewhat amplified diagnosis as follows: 



" Frondes bipinnatim divisse, pinnis patentibus, lobis seu pinnulis tota 

 basi insidentibus, interdum confluentibus, raro breviter auriculatis, 

 acuminatis vel obtusis, hie illic, prsecipue apice, dentieulatis, baud raro 

 sursum subf alcatis ; nervo medio sat valido, nervis secundariis sub angulis 

 acutis vel patentioribus orientibus, paulum supra basin dichotomis et 

 repetito-dichotomis, tenuibus et tenuissimis." ^ 



Later this author ^ abandons Cladophlehis in the belief that the fertile 



^Saporta, Pal. France, ser. ii, Vegetaux, PI. Jurass., t. i, 1873, pp. 298, 299. 



2 ScMmper, Pal. Veget. t. lii, 1874, p. 503. 



^ Schimper in Zittel's Handbucli der Palseontologie, Abth. ii, 1890, pp. 99, 100. 



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