DIOONITES. 37 



genus Pterophyllum he includes fronds with pinnce vertically 

 attached to the side of the rachis, and having truncate apices. 

 His genus Ctenophyllutn, 1 which includes certain forms often 

 referred to Pterophyllum, is defined as follows: "Folia linealia, 

 gracilia ; foliolis lateri rachis superior! oblique adfixis, ssepius 

 oppositis, linealibus, obtusis, basi retro folium infrapositum de- 

 fleuntibus, coriaceis, tenuiter et parallele nervosis." 



Saporta departs somewhat from the definitions given by other 

 authors, 2 and restricts Pterophyllum to fronds with pinnae attached 

 to the side of the rachis, and which are distinct one from another, 

 not fused laterally at the base, and having truncate apices. 

 Feistmantel, 3 on the other hand, in speaking of Zamites proximus, 

 Feist., points to the separate pinnae, which are not connected 

 at the base, as a feature inconsistent with the inclusion of the 

 plant in the genus Pterophyllum. Nathorst 4 has described 

 certain plants from Bjuf as possibly species of Pteropliyllum ; 

 but to express the absence of perfectly satisfactory evidence, he 

 prefixes a query to the generic name. More recently, this 

 author has called attention to the lateral insertion of the pinnao 

 as an essential character of Pterophyllum, and a convenient 

 distinguishing feature from Nilssonia? In Zittel's Handbuclif 

 the lateral attachment of the pinnaB, which may or may not be 

 distinct at the base, and their rounded or truncate apices are given 

 as important generic marks. It is suggested that possibly such 

 a frond as Pterophyllum Dunkerianum, Go'pp., ought not to be 

 included in the genus Pterophyllum, because of the insertion of 

 the segments on the upper surface of the frond axis. Solms- 

 Laubach 7 refers to P. Jaegeri, Brong., as an example of one 

 form of Pterophyllum frond, and in another place 8 calls attention 

 to the Nilssoma-like form of some species of the same genus, 

 which agree with other examples of Pterophyllum in the lateral 

 insertion of the leaf lamina. 



1 Trait, pal. veg. vol. ii. p. 127. 



2 Loc. cit. p. 43. 



3 Foss. Fl. Gond. vol. i. ser. ii. 2, p. 115. 



* (A. 1), pt. ii. pp. 69-72. 



5 (A. 3), Denkschr. k. Ak. "Wiss. math.-nat. Cl. vol. Ivii. p. 6. 



(A.), p. 224. 



7 Fossil Botany, p. 88. 



8 Ibid. p. 139. 



