546 PTERIDOSPERMS, ETC. [CH. 



naher bekannt'." An examination of the figures reveals 

 nothing as to the nature of the " sori." The specimens are 

 considered by Salfeld to afford decisive evidence against the 

 view that Lomatopteris and Thinnfeldia are generically identical. 

 Nothing has so far been published which constitutes a valid 

 argument in favour of retaining Schimper's generic name. 



Cycadopteris. 



Zigno ^ founded the genus Cycadopteris on Italian Jurassic 

 impressions regarded by Schimper as indistinguishable from 

 Lomatopteris. As Solms-Laubach^ points out, the supposed 

 sori of Cycadopteris described by Zigno are not convincing. 

 There appear to be no satisfactory reasons fOr separating 

 Cycadopteris from Lomatopteris, nor do the fronds described 

 under these names exhibit any important differences from 

 Thinnfeldia. 



Ptilozamites. 



Nathorst* founded this genus on a remarkable series of 

 specimens from the Rhaetic Coal-beds of Scania and assigned 

 it to the Cycadophyta. The species Ptilozamites Heeri may be 

 taken as a representative type. The leaves are linear and 

 simply pinnate. In the example shown on a much reduced 

 scale in fig. 361 the frond is 53 cm. long and 2"1 cm. broad. 

 The upper edge of each pinnule is straight or slightly concave ; 

 the lower edge is rounded ; the veins are slightly divergent 

 and dichotomously branched (fig. 356, E, p. 539). In some of 

 Nathorst's specimens the broa'd rachis is forked as in many 

 Thinnfeldias. 



As a comparison of fig. 356, A and E, shows, the pinnules 

 of some specimens of Thinnfeldia odontopteroides are identical 

 with those of Ptilozamites. In the latter genus the rachis is 

 either unbranched or occasionally forked, while in Thinnfeldia 

 the branching may be of the dichotomous or pinnate type. In 

 Ptilozamites the segments appear to be always without a mid- 



1 Salfeld (09) p. 34. 2 Zigno (56) A. 



3 Solms-Laubach (91) A. p. 114. " Nathorst (78). 



