562 PTERIDOSPERMS, ETC. [CH. 



for an entirely different plant led Dawson* to institute the 

 genus Archaeopieris. The genus Archaeopteris may be defined 

 as follows : 



Fronds bipinnate, reaching a considerable length (90 cm.) ; the stout 

 rachis bears long linear pinnae; sterile pinnules obovate or cuneate with 

 an entire, lobed, fimbriate, or laciniate lamina traversed by divergent 

 dichotomously branched veins. The fertile pinnae usually occur on the 

 lower part of the rachis; pinnules with a much reduced lamina bear 

 numerous fusiform or oval exannulate sporangia (fig. 369, A, E, H), sessile 

 or shortly stalked, singly, or in groups of two or three. The base of the 

 petiole is characterised by a pair of partially adnate stipules (fig. 369, C, D), 

 and single pinnules or scales occur in some species on the rachis between 

 the pinnae and on the petiole. 



Archaeopteris hibernica (Forbes). Figs. 368, 369, A — C. 



The specimen from Kilkenny represented in fig. 368 has 

 a length of over 80 cm. The upper pinnae bear numerous 

 imbricate obovate pinnules (fig. 369, A, B) with an entire or 

 very slightly fimbriate margin, while on the shorter lower 

 pinnae the ultimate segments are reduced to a slender axis 

 bearing numerous fusiform sporangia, 2 — 3 mm. in length. 

 Kidston^ has pointed out that sporangia occasionally occur 

 on the edge of ordinary pinnules, and he first recognised the 

 stipular nature of the scale-like appendages which Baily noticed 

 on the swollen petiole base (5 cm. broad) of the Irish species 

 (fig. 369, C). Restorations of Archaeopteris hihernica have been 

 figured by Baily^ and by Carruthers*, but the description of 

 the fertile pinnae by the latter author requires modification in 

 the light of Kidston's description of the Dublin specimens. 



Archaeopteris is recorded from Upper Devonian rocks of the 

 South of Ireland, Belgium, Germany, Southern Eussia, Bear 

 Island, and Ellesmere Land in the Arctic regions, Canada, 

 Pennsylvania, and elsewhere. Many of the specimens described 

 under different names bear a close resemblance, which in some 

 cases probably amounts to specific identity, to A. hihernica. 



1 Dawson (71) A. p. 48 ; (82). 



2 Kidston (91^) p. 30, PI. in. ; (06) p. 434. 



3 Baily (75) PI. xxviii. •» Carruthers (72^) PI. n. 



