Dl' Marti us on Antediluvian Plants. 275 
culate or erose margin of the scales, must of course shew the 
place from whence the upper part of the leaves has proceeded. 
After premising this much with regard to the structure of the 
stems, we now give the character of Yiiccites : 
A woody stem^ simple or branched above, with branches 
nearly equalling the stem in thickness, covered with plane or 
gibbous scales, crenated or erose at the margin, imbricated up- 
wards, and tlience not distinct beneath, destitute of cicatrices. 
I am acquainted with three species of this genus, dug up from 
the coal-mines of St Imbert, and remarkable for the still persist- 
ent covering of scales reduced to charcoal. 
1. Yucciies microlepis. 
With triangular scales, twice as broad as long, having their 
margins, which are entire, meeting at an acute angle, plane, im- 
pressed with a subhemispherical pit from the middle to the base. 
2. Yuccites spliterolepis. 
With triangular scales, twice as broad as long, their eroded 
margins meeting so as to form the segment of a circle, gibbous 
on the back, the gibbosities triangular, attenuated downwards. 
5. Yuccites trigonolepis. 
With triangular scales, having their straight, entire margins 
meeting at an acute angle, elevated on the back, the gibbosities 
attenuated upwards. 
Figured by Succow, PI. 18. f. 15. 
This species is remarkable for the size of its scales. Schlot- 
heim’s Palmacites affinis^ PI. 15. should perhaps be referred to 
this ; but as the figure seems to have been taken from a speci- 
men which had been deprived of its bark, we can only form a 
doubtful opmion with regard to it. The reason that the tex- 
ture of the scales is found best preserved in these petrifactions, 
is, that the leaves, when involved in the general destruction, of- 
fered more resistance on account of their fleshy or cartilagino- 
fibrous structure, and, being converted into charcoal, adhered 
firmly to one another and to the petrified parts ; while the in- 
ternal parts of the stem, by absorbing the mud with which 
every thing was then invested, assumed a stony nature. Thus, 
in the greater number of specimens, we see the scales themselves; 
