140 DICTYOPHYLLUM 



elusive as regards the claim of Bunker's generic title to be 

 retained. I expect that the discovery of more perfect examples 

 of what Dunker designated Hammannia may lead to the con- 

 clusion that this genus represents a form of Dictyophyllum. A 

 comparison of Schenk's figures of Hammannia dichotoma, Dunk., 

 and Nathorst's of Dictyophyllum Nilssoni, Brong., 1 var. intermedium, 

 in his "Flora of Sweden," is very suggestive of the generic identity 

 of the two species. 



Dictyophyllum Roemeri, Schenk. 



1871. Dictyophyllum Hoemeri, Schenk, Palaeontographica, vol. xix. p. 224, 



pi. xxxi. fig. 3. 

 1892. ?Hausmannia Forchhammeri, Bartholni, Bot. Tids. Bot. For. 



Kjovenhavn, vol. xviii. Heft i. p. 26, pi. xi. figs. 4 and 4. 



Type. Small sterile portion of a frond. In the University of 

 Wiirzburg Collection. 



Schenk defines this species as follows : 



"Folia . . . ? lacinise margine crenate, crense integrse, nervi 

 primarii validi, secundarii angulo recto egredientes, rami et 

 ramuli in rete areas irregulariter polygonas formantes conjunct!." 

 In the fragments from the Sussex Wealden the sori are fairly 

 clearly shown. 



Habit of the complete frond unknown ; the lamina traversed by 

 strong palmately-disposed veins which probably constitute the 

 central axes of the leaf segments. 



The secondary veins form a reticulate structure, and in the larger 

 meshes there are smaller reticulate branches; the sori scattered 

 on the lower surface of the leaf; in some of these the sporangia 

 appear to have a fairly regular arrangement in groups of four or 

 more round a common centre. 



Schenk was the first to record this genus of the Dictyopteridece 

 from Wealden rocks; the present species repeats such characters 

 as are more distinctly shown in the much more perfect and larger 

 fronds found in Rhaetic and Jurassic strata. So far as the nature 

 of the species is indicated by the few specimens from German 

 and English beds, it appears to agree with Dictyophyllum 



1 PI. iv. 



