.DICT YOPHYUUM. 121 



Andrae's genus Protorhipis was described in 1853 ' from the 

 Jurassic rocks of Steierdorf under the name Protorhipis Buchii: 

 this differs from Hausmannia dichotoma of Dunker in having 

 -■a broader suborbicular leaf with an irregularly dentated margin. 

 Some foSsils figured by Bartholin from Bornholm as Hausmannia 

 ForcMammeri ^ are in part apparently identical with Andrae's 

 Protorhipis Buchii, while others agree equally well with Bunker's 

 "Wealden type. Zeiller has recently pointed out that Bartholin's 

 specimens should bo referred to Protorhipis,'^ and it seems clear 

 that Andrae's genus should include fronds of the Hausmannia 

 tidehotoma type. As Zeiller has demonstrated by photographs 

 and several good examples of Steierdorf specimens, the genus 

 Protorhipis agrees remarkably closely with the recent genus 

 Dipteris, to which it is undoubtedly very nearly related. It is 

 convenient to retain the name Protorhipis for certain species of 

 "Wealden and Jurassic ferns which agree in the form of the 

 frond with Dipteris, and are somewhat smaller than the typical 

 Bietyophyllwm fronds. While it is not difficult to distinguish 

 between Bictyophyllum and Protorhipis in the case of good 

 specimens, it is practically impossible to do so if we have only 

 fragments of fronds. 



If we retain Camptopteris in !N^athorst's sense, the only other 

 generic names of those we have mentioned which should be 

 retained are, in my opinion, Bictyophyllum, Protorhipis, and 

 possibly Clathropteris. 



As Brongniarf long ago noticed, there is a striking similarity 

 between the fronds of some species of Polypodium — referred to 

 a special subgenus Brynaria — and the leaves of Bictyophyllum ; 

 this resemblance, however, does not extend to the habit of the 

 frond as a whole. As regards the shape of the frond, there is 

 a, still closer resemblance between Bipteris and Bictyophyllum, and 

 -a stUl more striking similarity between Bipteris and Protorhipis. 



' Andrae (53), p. 35, pi. viii. 



2 Bartholin (92), p. 26, ph. xi. and xii. 



' Zeiller (97), pi. xxi. 



* Brongniart (28i), p. 62. 



