560 PTERIDOSPERMS, ETC. [CH. 



Callipteridium. 



The name Callipteridium, created by Weiss ^ as a sub-genus 

 of Odontopteris, is applied by Zeiller and other authors to a 

 few Upper Carboniferous and Permian species characterised by 

 the occurrence of simply pinnate pinnae on the main rachis 

 between the bipinnate primary pinnae. Single pinnules are 

 borne directly on the rachis of the primary pinnae between the 

 pinnate branches. The form and venation of a typical pinnule 

 are shown in fig. 366, B. Callipteridium pteridium, originally 

 recorded by Schlotheim as Filicites pteridius^, has been fully 

 described by Renault and Zeiller from unusually large specimens 

 found in the Commentry Coal-field^, This species illustrates 

 the peculiar morphological features of the genus. The main 

 rachis of the tripinnate fronds, several metres long, shows a 

 combination of dichotomous and pinnate branching; from the 

 zigzag and forked axis are given off bipinnate pinnae and, 

 between these, shorter pinnate branches. The pinnules closely 

 resemble those of Callipteris conferta but reach a greater length; 

 the pinnules borne on the rachises of the lateral branches differ 

 from the others in their broader base and more triangular lamina. 



No fertile specimens have been found. It is probable that 

 Callipteridium, was not a true fern, and that White^ is correct 

 in including it among the Pteridosperms. 



Archaeopteris. 



In 1852 Forbes^ published a brief description of some 

 supposed fern fronds, found by the Geological Surveyors of 

 Ireland in Upper Devonian rocks of Kilkenny, under the name 

 Cydopteris hibernica. The Irish specimens were more fully 

 described by Baily" in 1858. Fronds of the same type were 

 referred by other authors to Cydopteris, Adiantites or Noeg- 

 gerathia, until Schimper^ proposed the generic name Palaeo- 

 pteHs on the ground that the fronds described by Forbes and 



1 WeiBR, C. E. (70). 2 Schlotheim (20) A. p. 406. 



3 Renault and Zeiller (88) A. PI. xix. * White (05^) p. 388. 



» Forbes (53) p. 43. « Baily (59) p. 75. ' Schimper (69) A. p. 473. 



