MATONIDITJM. 63 



pinnatifida. ITervi primarii excurrentes, secundarii angulo subrecto 

 egredientes dichotomi, ramuli simplioes. Sori biseriales oblongi 

 indusiati. Sporangia receptaculo in ramulo affixa. Annulus 

 obliquus." 



When this fossil genus was first instituted by Schenk there 

 was only one species recorded of the recent Mafonia, and the 

 characteristic and peculiar habit of that species, M. pectinata, Br., 

 suggested the term Matonidium for fronds of similar form. It 

 is important, in speaking of this similarity of form and of the 

 Matonia-like habit, to remember the recent addition of a second 

 species, M. sarmentosa, Baker,' which has an entirely different 

 habit to that which has always been regarded as typical of the 

 genus. Baker's figure of this new species shows in a striking 

 manner the danger of trusting to sterile portions of fronds in 

 the determination of generic affinity. 



1. — Matonidium Gbpperti (Ett.). 



1843. Cycadites Althausii, Bunker, Progr. p. 7. 



1846. Pecopteris Althausii, Dunker, 'Wealdenbildung, p. S, pi. ii. fig. 2. 



recopteris polydactyla, Dunker, loe. ait. p. 5, pi. vii. fig. 4. 



Fecopteria Conybeari, Dunker, loc. cit. p. 7, pi. ix. figs. 8 and 8«. 



Alethopteris elegcms, Dunker, loc. cit. p. 8, pi. vii. fig. 7. 



1849. Pecopteris polydactyla, Brongniart, Tableau, p. 107. 

 Peeopteris Conybeari, Brongniart, loc. cit. p. 107. 

 Pecopteris Althausii, Brongniart, loc. cit. p. 107. 

 Pecopteris elegims, Brongniart, loc. cit. p. 7. 



1850. Pecopteris polydactyla, TJnger, Gen. spec, plant, foss. p. 177. 

 Pecopteris Conybeari, Unger, loc. cit. p. 177. 



Pecopteris Althausii, Unger, loo. cit. p. 176. 

 Alethopteris elegans, Unger, loc. cit. p. 147. 

 1852. Alethopteris Gopperti, Ettingshausen, Abh. k.-k. geol. Eeichs. vol. i. 



Abtli. iii. No. 2, p. 16, pi. t. 

 1854. Alethopteris elegcms, Morris, Brit. foss. p. 2. 



1864. Pecopteris poh/daotyla, Leokenby, Quart. Joum. Geol. Soo. Yol. xx. 

 p. 80, pi. xi. figs. \a and 16. 



1869. Zaccopteris Gopperti, Scbimper, Trait, pal. veg. vol. i. p. 682, Atlas, 



pi. XXX. figs. 5-8. 



1870. Pecopteris Althausii, Trautschold, Nouv. Mem. Soo. Nat. Moscou, 



vol. xiii. p. 28, pi. xix. figs. 3d and e. 

 ? Pecopteris explanata, Traatschold, loc. cit. p. 32, pi. xix. fig. 7. 



1 Annals Bot. vol. v. 1890-91, p. 191, pi. xiv. (First described in Joum. 

 linn. Soc. vol. xxiv. 1888, p. 256.) 



