CONIOPIEEIS. 105 



Slave a transition from a pinnule of the racemosa type to others 

 •of the simplex form. The pinna shown in Kg. 4 of the same plate 

 recalls 8. nephroearpa of Bunhury, and from this type we pass 

 hy gradual transitions, marked by an increasing reduction of the 

 ilamina, to the form represented in Pigs. 6 and 8, PL XVII. 

 These details are more fully dealt with in the description of the 

 individual specimens. 



The same type of fertile segment is found also in some of 

 Heer's Siberian ferns referred by him to Thyrsopteris and 

 Dicksonia ; e.g., B. clmipes, T. Maakiana, and T. Mwrrayana. 

 -Zigno's species Hymenophyllites Zeckenlyi, from the Italian Oolite, 

 is another form closely resembling the fertile pinnse of Coniopteris 

 hymenophylloides. Finally, Eaoiborski figures some fertile leaves 

 as Dicksonia Seerii, which are probably identical with the English 

 species ; and his species B. Zarectnyi might also be reasonably 

 referred to the same specific type. 



There are several recent species with which Coniopteris hymeno- 

 phylloides may be compared. The fertUe pirmse of Thyrsopteris 

 elegans, Kze.,' are practically identical with some examples of the 

 fossil species (e.g., PI. XVII. Figs. 6 and 8 ; PI. XXI. Figs. 3 and 

 3fl) ; there is also a fairly close agreement between the sterile 

 .segments of the fossU and recent types. The fertile segments of 

 Bicksonia Bertervana, Hook. (Text-fig. 13), have the same form as 

 those of Thyrsopteris ; the two-lipped indusium of the former is 

 a point of difference which may be easily overlooked. It is 

 interesting to note the striking difierence between the sterile pinnte 

 of the Bicksonia shown in Text-fig. 13 and the Sphenopteroid 

 pinnae of Thyrsopteris and Coniopteris hymenophylloides. There can 

 be little doubt that Thyrsopteris elegans may be regarded as an old 

 tjrpe of fern which was widely distributed in Mesozoic times. 



Among other recent ferns which bear a strong likeness to 

 Coniopteris hymenophylloides we may mention Bicksonia arhorescens, 

 li'Her., and Balantium culcita (L'Her.) ; also some species of 

 Ba/vallia, e.g., Bavallia canariensis, Sm., B. Wilfordii, Baker, etc. 

 As illustrating a variation in the form of the fronds in the same 

 ylant, even greater than that in Coniopteris hymenop 



' For figures of this fern vide Engler & Prantl (99), p. 122 ; Hooker (42), 

 jpl. xliv. A. 



