140 bictyophillum: 



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

 retained. I expect that the discoYery of more perfect examples 

 of what Dunker designated Hausmannia may lead to the con- 

 clusion that this genus represents a form of Biotyophyllum. A 

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

 and Nathorst's of Biotyophyllum Nilssoni, Brong./ var. intermedium, 

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

 of the two species. 



Dictyophyllum Eoemeri, Schenk. 



1871. Dietyophyllum Soemeri, Schenk, Palseontograpliioa, vol. lix. p. 224, 



pi. xnx. fig. 3. 

 1892. ?Sauamannia Forehhammeri, Bartholni, Bot. Tids. Bot. For. 



KjovenhaTn, vol. xviii. Heft i. p. 26, pi. xi. figs, i and ia. 



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

 Wiirzburg Collection. 



Schenk defines this species as follows : — 



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

 primarii validi, secundarii angulo recto egredientes, rami et 

 ramuli in rete areas irregulariter polygonas formantes conjuncti." 

 In the fragments from the Sussex Wealden the sori are fairly 

 clearly shown. 



Hahit 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 arrEingement in groups of four or 

 more round a common centre. 



Schenk was the first to record this genus of the Bictyopteridets 

 from Wealden rocks; the present species repeats such characters 

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

 fronds found in Eheetic 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 Biotyophyllum 



1 PI. iv. fig. 8. 



