138 DICTYOPHYLLUM 
Genus DICTYOPHYLLUM, Lindley and Hutton. 
[Fossil Flora, vol. ii. 1833-35, pl. civ. p. 65.] 
This generic name was proposed by Lindley and Hutton for a 
plant originally described by Phillips from the Upper Sandstone 
and Shale of the Yorkshire Oolite; these authors describe the type 
specimen, Dictyophyllum rugosum, as a “ pinnatifid leaf belonging 
to some exogenous plant.”” The older name, Phyllites, having been 
‘‘taken as the receptacle of all sorts of leaves,” the new one, 
Dictyophyllum, is proposed for ‘‘ doubtful Dicotyledonous leaves of 
common reticulated structure.””! Subsequent writers have retained 
the proposed name, although the discovery of sori on leaves with 
distinct Dictyophyllum characters has necessitated an entirely new 
definition of the genus. 
The few fragments in the Wealden Collection add nothing to 
our knowledge of this fern, for which we are chiefly indebted to 
Schenk; we may, therefore, adopt his definition of the genus? :— 
‘Folia sterilia et fertilia conformia pedato-pinnata, lacinice 
pinnatifide. Nervi primarii radiantes, secundarii angulo recto 
egredientes excurrentes apice in rete soluti, tertiarii angulo recto 
egredientes maculas inequaliter hexagonales formantes pluri- 
seriales, costales majores, relique minores, omnes appendicibus 
anastomosantibus in maculas parvas partiti. Sori per totam 
paginam folii inferiorem sparsi, rotundi, sporangia pauca annulo 
multiarticulato instructa, spore tetraédrice globose.” 
Schimper,’ Saporta,‘ and others include this genus with other 
closely allied forms in the family Dictyopteridee. 
Saporta, in the first volume of his ‘ Plantes Jurassiques,” 
discusses the points of difference between Dictyophyllum, Thaumato- 
pteris, and Clathropteris; these differences depend chiefly on the 
form of the frond segments and the details of venation. In dealing 
with small pieces of a frond it is not always easy to decide which 
genus should be chosen.  Clathropteris is, in most cases, readily 
distinguished by the rectangular nature of the venation, but in a 
1 Foss. Flor. vol. ii. p. 66. 
2 Fl. foss. Grenz. Keup. Lias, p. 76. 
3 Trait. pal. vég. vol. i, p. 617. 
4 Pal. Fran¢. vol. i. p. 3265. 
