CONIOPTERIS. 105 



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

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

 recalls S. nephrocarpa of Bunhury, and from this type we pass 

 by gradual transitions, marked hy an increasing reduction of the 

 lamina, to the form represented in Figs. 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., D. clavt'pes, T. Maakiana, and T. Murray an a. 

 Zigno's species Hymenophyllites Zeckenbyi, from the Italian Oolite, 

 is another form closely resembling the fertile pinna3 of Coniopteris 

 hymenophylloides. Finally, Raciborski figures some fertile leaves 

 as Dicksonia JZeen'i, which are probably identical with the English 

 species ; and his species D. Zarecznyi might also be reasonably 

 referred to the same specific type. 



There are several recent species with which Coniopteris hymeno- 

 phylloides may be compared. The fertile pinnae of Thyrsopteris 

 elegam, Kze., 1 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 fossil and recent types. The fertile segments of 

 Dicksonia 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 difference between the sterile pinna? 

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

 pinnao of Thyrsopteris and Coniopteris hymenophylloides. There can 

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

 type of fern which was widely distributed in Mesozoic times. 



Among other recent ferns which bear a strong likeness to 

 Coniopteris hymenophylloides we may mention Dicksonia arborescens, 

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

 Davallia, e.g., Davallia canariensis, Sm., D. Wilfordii, Baker, etc. 

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

 even greater than that in Coniopteris hymenophylloides, 



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

 pi. xliv. A. 



