TODITES. 89 



Pinnules attached by a broad base, closely set on tbe axis of 

 the pinna, but the longer fertile segments of the larger pinnae are 

 iarther apart and more open in their arrangement. Slightly 

 falcate, the side towards the rachis is strongly convex, and the 

 outer margin is straight or concave, and bulged outwards towards 

 "the base of each segment ; the apex of the pinnules is acute ; 

 the margin is ia some cases, especially in the larger segments, 

 slightly lobed. In the larger pinnaa the pinnules may be between 

 l'5-2 cm. in length. Towards the distal tapering end of the 

 piunse the pinnules are more falcate, and assume a short deltoid 

 form (as in Peoopteris dentata, L. & H.), and the acute apex is 

 ■directed forward. The venation is of the CladopMelis type ; each 

 segment being traversed by a midrib from which spring forked 

 secondary veins, and the midrib itself breaks up into dichotomously 

 branched veins towards the tip of the segments. 



The fertile pinnules have usually the same form as the sterile, 

 but in the larger segments the breadth is often less in proportion 

 "to the length than in the sterile segments, and the margin of the 

 former often shows a tendency towards irregular lobing. 



The sporangia are large and circular, and of the Osmundaceous 

 tjrpe ; they usually cover the whole of the under surface of the 

 fertile segments, as in Todea. 



The long list of synonyms demonstrates the confusion with 

 regard to the nomenclature of this common and characteristic 

 •Jurassic fern. The confusion is considerably increased by the fact 

 that the fern to which Brongniart gave the name Peoopteris 

 whithiensis — a species usually considered to have been very widely 

 distributed during the Jurassic period — is not identical with the 

 plant to which Lindley & Hutton and several other authors applied 

 the same designation. Brongniart's Peoopteris whithiensis I have 

 no doubt is specifically identical with his Peoopteris Williamsonis, 

 and with the specimen described under this name by Liudley 

 and Hutton. On the other hand, the Peoopteris whithiensis of 

 Lindley & Hutton and of several other writers is, I believe, 

 specifically identical with Peoopteris dentioulata of Brongniart; 

 but this question is more fully discussed under the latter species. 

 Peoopteris tenuis of Brongniart is included in the above synonymy 

 as identical with Todites Williamsoni, as the form of the pinnules 

 and the habit of the frond appear to agree exactly with the 

 •characters of that species. Nathorst has expressed similar views 



