168 HISTORICAL PALZZVONTOLOGY. 
The so-called Sig¢//arioids, represented mainly by Svgz//aria 
itself (fig. 111), were no less abundant and characteristic of the 
Carboniferous forests than the Lepzdodendra. ‘They commence 
their existence, so far as known, in the Devonian period, but 
they attain their maximum in the Carboniferous ; and—unlike 
the Lepidodendroids—they are not known to occur in the 
Permian period. They are comparatively gigantic in size, 
often attaining a height of from thirty to fifty feet or more; 
but though abundant and well preserved, great divergence of 
opinion prevails as to their true affinities. The zame of Sigil- 
larioids (Lat. szg//a, littie seals or images) is derived from the 
fact that the bark is marked with seal-like impressions or leaf- 
scars (fig. III). 
Externally, the trunks of Svg¢//aria present strong longitudinal 
ridges, with vertical alternating rows of oval leaf-scars, indicating 
Fig. 111.—Fragment of the external surface of Sig7/laria Greseri, showing the ribs and 
leaf-scars. The left-hand figure represents a small portion enlarged. Carboniferous, 
Europe. 
the points where the leaves were originally attached. The trunk 
was furnished with a large central pith, a thick outer bark, and 
an intermediate woody zone,—composed, according to Dawson, 
partly of the disc-bearing fibres so characteristic of Conifers ; ; 
but, according to Carruthers, entirely made up of the “ scalari- 
form ” vessels characteristic of Cryptogams. ‘The size of the 
pith was very great, and the bark seems to have been the most 
durable portion of the trunk. Thus we have evidence that 
in mary cases the stumps and “stools” of Svgi//ari@, standing 
