spnExopnYLLUM. 35 



character which led Royle, 1 in his original description published in 

 1833, to institute a new genus, Trizygia, for its reception. There 

 has since been some difference of opinion as to whether this con- 

 clusion should be maintained. M'Clelland, 2 in 1850, reverted to the 

 generic title Sphenophyllum, while others, especially Feistmantel in 

 his later memoirs, have adopted Royle's genus. In 1891, however, 

 M. Posniaski discovered specimens possessing tbe same characteristic 

 arrangement of the leaves as the Indian species in the Carboniferous 

 beds of Monte Pisano, and Professor Zeiller 3 has since pointed out 

 that Sphenoph}-llums with all the generic characters of Trizygia 

 occur both in the Coal-measures and tbe Permian. Consequently 

 there seem to be no good reasons for retaining Koyle's genus, and 

 Mr. Seward and others have adopted Zeiller's conclusion. 



1. Sphenophyllum speciosum (Royle). 

 (PL I, Pigs. 1, la.) 



1833. Trizygia speciosa, Royle, Illust. Bot. Hinial. Mounts., p. xxix*, pi. ii, 



fig. 8. 

 1845. T. speciosa, Unger, Synopsis Plant, foss., p. 114. 

 1850. Sphenophyllum speciosa, M'Clelland, Rep. Geol. Surv. India, p. 54, 



pi. xiv, fig. 5. 

 S. trizygia, Unger, Gen. et Spec. Plant, foss., p. 71. 

 1860. Sphenophyllum, Oldham, Mem. Geol. Surv. India, vol.ii, pt. 3, p. 326. 

 1865. Trizygia, Blanford. Mem. Geol. Surv. India, vol. iii, pt. 1, p. 31. 

 1876. Sphenophyllum trizygia, Feistmantel, Rec. Geol. Surv. India, vol. ix, 



pt. 3, p. 70. 

 S. trizygia, Feistmantel, Journ. Asiat. Soc. Bengal, vol. xlv, pt. 2, 



p. 342, pi. xv. tigs. 1, 2, 2a. 



1879. Trizygia, Feistmantel, Rec. Geol. Surv. India, vol. xii, pt. 3, p. 163. 



1880. T. speciosa, Feistmantel, Flora Gondw. Syst., vol. iii, pt. 3, p. 69, 



pi. xi a ; pi. xii a, figs. 1, \a, 2. 

 1882. T. speciosa, Feistmantel, Flora Gondw. Syst., vol. iv, pt. 1, p. 22. 

 1886. T. speciosa, Feistmantel, Flora Gondw. Syst., vol. iv, pt. 2, p. 22. 

 1891. Sphenophyllum speciosum, Zeiller, Bull. Soc. Geol. France, ser. in, 



vol. xix, p. 673. 

 1898. S. speciosum, Seward, Fossil Plants, vol. i, p. 411, text-fig. 111. 



1900. 8. speciosum, Zeiller, Elem. Paleobot., p. 140. 



1901. 'Trizygia, Kidston, Trans. Nat. Hist. Soc. Glasgow, n.s., vol. vi, 



p. 129. 

 Sphenophyllum speciosum, Arber, Geol. Mag., dec. iv, vol. viii, p. 546. 



1 llovle (33), p. xxix*. 



2 M'Clelland (50). 



3 Zeiller (91), p. 673. 



