140 FILICES. 



incisions into pinnae which touch one another and may be of unequal breadth. 

 Similar conditions have been noticed above in the case of species of Ptero- 

 phyllum ; but in these, as Nathorst rightly observes, the lamina is inserted 

 exactly laterally, whereas its lines of insertion in true Nilssoniae are moved 

 quite to the upper side of the rhachis and brought close together. The form 

 also of the individual segments shows not unimportant differences. Delicate 

 unbranched nerves run from the strong midrib perpendicularly to the margin 

 of the leaf, and are separated from one another by raised strips. If in spite 

 of all this agreement with Pterophyllum I still prefer to treat of this genus 

 among Ferns, it is because in Schenk's l figures of the plant we see portions 

 of leaves in which there are small roundish protuberances on the under side 

 of the leaf in regular rows and parallel to the nervation ; these he considers 

 to be remains of sori, and though this has not been certainly proved, yet 

 from the regular disposition of these objects I consider Schenk's view more 

 probable than that of Saporta 2 , who takes them for leaf-fungi. 



A genus with the nervation of Neuropteris and calling for notice 

 in this place is Thinnfeldia, Ett., which in its typical species belongs to 

 the Rhaetic deposits and to the angulatus-beds of the Lower Lias. It 

 was first accurately described by Ettingshausen 3 from Steierdorf in the 

 Banat, and next by Schenk 4 from the neighbourhood of Bayreuth. A 

 detailed description of it, accompanied with good figures, is to be found also 

 in Saporta 6 . Another species, Thinnfeldia crassinervis, has been described 

 by Geinitz 6 from the Rhaetic beds of the Argentine Republic. A species 

 from deposits in Australia above the Coal-measures has been referred by 

 O. Feistmantel 7 to this genus, but as it shows the nervation of Cyclopteris 

 it is a doubtful Thinnfeldia. The thick solid leaves of Thinnfeldiae are 

 simply pinnate ; the entire or lobed pinnae are connected together at the 

 base by a margin of tissue which accompanies the midrib. In Ettingshausen 

 and Geinitz they are represented with a forked division in the middle of 

 the lamina. The resemblance to Phyllocladus on which Ettingshausen 

 insists, and which Nathorst 8 also admits with some reserve, is, as Schenk 9 

 has shown, not very important. The nervation, that is to say, is essentially 

 different, it is the consistence only of the leaves which supplies a point of 

 comparison. After Schenk's excellent discussion of the question there 

 would be no reason for doubting that these leaves are the remains of Ferns, 

 if stomata were not found on both sides of them, and if the stomata were 

 not slightly sunk beneath the epidermis and walled round by the adjacent 

 cells which rise above them. The latter structure is very common in 

 Cycadeae and Coniferae ; it has never been observed by Schenk in Ferns. 



1 Schenk (3), t. 21, ff. i, 2. * de Saporta (4), vol. ii, p. 41. s von Ettingshausen (2). 



4 Schenk (3), tt. 26, 27, and Schimper (1), t. 85. * de Saporta (4), vol. i. p. 340. Geinitz 

 rt . 7 Feistmantel '1\ lit. f Nathorst 2 . Schenk (8\ 



