390 FILICALES [CH- 



resembling those of Clathropteris and Dictyophyllum, but differ- 

 ing in the form of the pinnae and in habit. The habit of the 

 type-species, C. spiralis, is shown in fig. 287. An examination 

 of the specimens in the Stockholm Museum convinced me of 

 the correctness of Nathorst's restoration^. Each of the forked 

 arms of the rachis bore as many as 150 — 160 long and narrow 

 pinnae characterised by an anastomising venation (fig. 282, C) 

 and by a spiral disposition due to the torsion of the axes. The 

 sporangia agree in essentials with those of Dictyophyllum. 



Hausmannia. 



A critical and exhaustive account of this genus has been 

 given by Prof. Von Richter^ based on an examination of 

 specimens found in the Lower Cretaceous rocks of Quedlinburg 

 in Germany. The name was proposed by Dunker' for leaves 

 firom the Wealden of Germany characterised by a deeply dissected 

 dichotomously branched lamina. Andrae subsequently instituted 

 the genus Protorhipis* for suborbicular leaves with dichoto- 

 mously branched ribs from the Lias of Steierdorf. A similar 

 but smaller type of leaf was afterwards described by Zigno^ 

 from Jurassic beds of Italy as P. asarifolius, and Nathorst^ 

 figured a closely allied form from Rhaetic rocks of Sweden. 

 While some authors regarded Hausmannia and Protorhipis as 

 ferns, others compared them with the leaves of Btdera (Gink- 

 goales); Saporta suggested a dicotyledonous affinity for 

 leaves of the Protorhipis type. The true nature of the 

 fossils was recognised by Zeiller', who called attention to the 

 very close resemblance in habit and in soral characters to the 

 recent genus Dipteris. A comparison of the different species 

 of Dipteris, including young leaves (fig. 231, p. 297), with those 

 of the fossil species reveals a very striking agreements There 

 can be no doubt, as Richter points out, that the names Haus- 

 mannia and Protorhipis stand for one generic type. 



1 Nathorst (062) p. i5_ z Biohter (06). 



3 Dunker (46) A. p. 12. * Andrae (53) A. 



« Zigno (56) A. ii. fig. 2. « Nathorst (78=) PI. ix. fig. 2. 



' Zeiller (97'*) p. 51. « Seward and Dale (01). 



