XXl] DIPTERIDINAE 383 



that of Matonia pectinata, affords another illustration of the 

 common occurrence in older ferns of a dichotomous system 

 of branching. The pinnae, characterised by circinate vernation, 

 reach a length of 60 cm. and are divided into linear lobes 

 inclined obliquely or at right angles to the pinna axis. The 

 whole of the under surface of the lamina may be covered with 

 sporangia, 4 — 7 sporangia in each sorus; the annulus is 

 incomplete and approximately vertical (fig. 282, D). The 

 rhizome is probably represented by the dichotomously branched 

 axis described by Nathorst from Scania as Rhizomopteris 

 major; the leaf-scars show a horse-shoe leaf- trace. 



Dictyophyllum Nathorsti Zeiller'. 



This type, represented by a splendid series of specimens 

 from the Khaetic beds of Tonkin, agrees very closely with 

 D. exile. It differs, however, in the basal parts of the pinnae 

 which are concrescent for a length of 5 to 8 cm. instead of free as 

 in D. exile ; and, to a slight degree, in the form of the ultimate 

 segments. In habit and in soral characters the two species are 

 practically identical. Each sorus contains 5 to 8 sporangia, 

 which are rather larger than those of Dipteriit. 



Dictyophyllum rugosum, Lind. and Hutt. Fig. 283. 



1828. Phlehopteris Phillipsii, Brongniart, Hist. veg. foss. p. 377, 

 PL cxxxii. fig. 3; PI. cxxxiii. fig. 1. 



1829. Phyllites nervulosis, Phillips, Geol. Yorks. p. 148, PI. viii. 

 fig. 9. 



1834. Dictyophyllum rugosum, Lindley and Hutton, Foss. Flor. ii. 



PI. CIV. 



1836. Polypodites heracleifolius, Goeppert, Foss. Farn. p. 344. 

 1849. Camptopteris Phillipsii, Brongniart, Tableau, p. 105. 

 1880. Clatkropteris whitbyensis, Nathorst, Berattelse, p. 83. 



This species, which is characteristic of Jurassic rocks, is 

 less completely known than the two types described above, 

 but in the form and venation of the pinnae there is little 

 difference between the Rhaetic and Jurassic plants. The leaves 

 of the Jurassic species appear to have been smaller and more 

 1 Zeiiler (03) p. 109, Pis. xxiii.— xxviii. 



