BICTTOPHYLLUM. 



119 



Geaus DICTYOPHYLLUM, Lindley & Hutton. 

 [Fos3. Plor. vol. ii. pi. civ. 1834.] 



The genus Bictyophyllum "was founded by Lindley & Hutton 

 as a designation for a pinnatifid leaf from the Yorkshire Oolite, 

 which they regarded as a doubtful Dicotyledon and named 

 Bietyophyllum rugosum. Plants agreeing closely with this species 

 have been placed by different authors in several genera, of 

 which the distinguishing characteristics are by no means clear. 

 "We have, for example, the genera Clathropteris, Thaumatopteris, 

 Camptopteris, Sausmannia, and Protorhipis applied to palmate 

 fern fronds of Mesozoic age, which agree in many respects 

 with Bictyophyllum, and with one another. The use of these 

 different names has not only led to much confusion, but has 

 also considerably exaggerated the diversity which exists among 

 the ferns referred to under the several genera. 



Goppert's genus Thaumatopteris has been wisely included by 

 Sohenk and some other writers in Bictyophyllum ; ' the examination 

 of several specimens referred to these genera in the Museums 

 of Berlin and elsewhere has convinced me that there are no 

 satisfactory grounds for retaining both generic names. 



The genus Clathropteris was iastituted by Brongniart in 1828 ' 

 for a plant which he had previously described from Scania under 

 the name Filicites menisooides ; ' the most striking characteristics 

 of this fern are its pinnatifid fronds and the regular square meshes 

 formed by the finer veins in the lamina. The best known species 

 of this genus is Clathropteris platyphylla (Gopp.),' of Ehsetic age, 

 the same type which Brongniart had described as Clathropteris 

 meniscoides. The main distinction between Clathropteris and 

 Bictyophyllum is the more regular and rectangular form of the 

 meshes formed by the secondary and tertiary veins of the former, 

 but in some fronds ' portions of the lamina exhibit the less regular 

 meshes characteristic of Bietophyllum. It would perhaps more 



1 Schenk, in Zittel (90), p. 138. 

 » Brongniart (28), p. 62. 

 ' Brongniart (25), p. 207, pi. xi. 

 * E.g. Schenk (67), pi. xvii. 



