CH. XXXVl] CYCADEOIDEA 367 



the genus Bennettites, placing it in a new tribe, tke Bennettiteae. 

 Some authors have followed Carruthers in the use of the 'family- 

 name Bennettiteae for a subdivision of the Cycadales equal in 

 rank to the Cycadaceae, while others, wishing to give greater 

 emphasis to the difference between the extinct and recent plants, 

 prefer to adopt the class-name Bennettitales. Carruthers regarded 

 Bennettites as occupying the same position in relation to other 

 Cycads as Taxus holds with regard to the cone-bearing members 

 of the Coniferae. The adoption of Bennettitales is intended to 

 convey the impression that the class is more distantly related to 

 the recent Cycads than is implied by the analogy of Taxus. 

 Nathorst^, as the result of his discovery of certain reproductive 

 organs associated with some Rhaetic fronds described as Dioonites 

 spectabilis, proposed a third subdivision, the Dioonitales, but he 

 subsequently^ restored the fronds to their original designation 

 Nilssonia pterophylloides, and on further examination found that 

 the supposed microspore-bearing organs were seeds. Nilssonia 

 fterofhylloides would therefore find a more natural place in the 

 class Nilssoniales instituted by Thomas*. 



BENNETTITALES. 



Cycadeoidea. Buckland. 



In 1827 Buckland* proposed the generic name Cycadeoidea for 

 some petrified stems from the Purbeck beds in the Isle of Portland 

 and published a description of two species, Cycadeoidea megalo- 

 fhylla and C. microphylla. Brongniart* considered Buckland's 

 term Cycadeoidea inappropriate and proposed in its place MantelUa, 

 the type-species being MantelUa nidiformis Brongn., the Portland 

 stem which Buckland a month or two later called independently 

 Cycadeoidea megalofhylla. Subsequently Brongniart* withdrew 

 Mantellia as it had been previously used by Parkinson for a 

 sponge and substituted Cycadites. Some years later Carruthers' 

 revived Mantellia for a type of Cycadean stem from Portland 



1 Nathorst (02) p. 23. ' Ibid. (09^) pp. 21, 23. 



' Thomas and Bancroft (13) p. 196. 



* Buckland (27) Proc. Geol. Soc. London, VoL i. No. 8, p. 80; (28). 

 6 Brongniart (28) A. p. 96. ' Ibid. (49) A. p. 59. 



' Carruthers (70) p. 678. 



