242 
ORGANIC REMAINS 
Adolphe Brongniart does not, however, admit the 
propriety of this distinction, but refers the fossil 
to his sub-genus Sphenopteris* “ The ramifi- 
cation of tlie fronds, indicated by the different planes 
in which the branches are disposed, appears to be 
very distinct from the mere distichous frond of the 
recent ferns,” and is another instance of the differ- 
ence existing between the vegetation of the ancient 
and modern condition of our planet, even in those 
genera that are in many respects analogous. The 
specimens present considerable variety both in the 
form, and disposition, of the fronds ; perhaps, here- 
after, these variations may be found sufficiently 
permanent and important, to constitute specific 
characters. This fern has been discovered in the 
hard calciferous sandstone, ironstone, shale, and 
clay ; it is generally in a carbonized state, and 
occurs in small portions, so that a knowledge 
of the entire form of the original ])lant is still 
a desideratum. It appears to have been very 
abundant, for no considerable block of stone is 
without traces of it : but it generally occurs in 
confused masses. 
* “ Cette fougere apparticnt an sous-genre que j’ai noninie Sphccnop- 
teris, et non an s. g. hymenopteris : le nom de 2>-^i^<>ioicles ne me parait 
pas trcs convenable en ce que cette plante differe totalcment dix genre 
psilotum ; si par cette raison vous me permettiez de lui donner le nom 
de Sp.MantcUi, on eviterait une comparaison qui ne me parait pas exacte, 
et on consacrerait le nom de la personne qui a la premiere prouv^ la 
presence de fougeres dans des terrains aussi inodernes.” — Extract of a 
Letter from M. Adolphe Brongniart to the Author. 
