156 GEOGNOSY AND GEOLOGY. 
transversely they never embrace the stem as in monocotyledons. The 
woody vessels which pass from the stem into the petioles, form regular and 
characteristic figures. The leaf scars are in parallel longitudinal rows. 
The stem supports a crown of simply or doubly pinnate leaves. The only 
possible means which we have at our command for classifying fossil ferns 
consists in the arrangement of the nervures. 
Sphenopteris has _ or tri-pinnate leaves, with leaflets airing deeply 
lobed, and the nervures radiating nearly from the base. 8S. Schlotheimii 
(pl. 37, fig. 60) is especially abundant in the Saarbrtick coal beds. * 
The bipinnate fronds of Odontopteris have thin leaflets, adherent by their 
entire base, which is never contracted, nervatures simple or dichotomous, 
all equal, proceeding from the rachis; central nervure indistinct: O. minor 
(pl. 87, fig. 61). 
The coal strata are filled with vast quantities of gigantic stems of ferns ; 
they have been found over 40 feet long and a foot in diameter. Their leaf 
scars are in parallel longitudinal rows, but are in much larger quantity than 
others in allied forms. Their thin carbonized bark readily falls off, exhibiting 
the casts of the scars. These are known as Sigillaria, of which a stem is 
figured in fig. 62; fig. 63 is a piece of the same with the bark removed ; 
jig. 64, an enlarged view of the leaf scars both above and below, or within 
and without the bark. 
Stems of Lycopodiacez are also found, hardly yielding in dimensions to 
those of Sigillaria. Thus we have Lepidodendron distinguished from the 
last by the spiral arrangement of the rhomboidal leaf scars. An entire stem 
of L. elegans (fig. 65) has been brought to light in the Bohemian coal 
mines: fig. 66 exhibits the arrangement of the leaves: fig. 67, the scars 
themselves. 
The coal formation, as far as known, is destitute of true dicotyledons ; 
doubtful forms, however, occur, which may or may not be such, as 
Sphenophyllum annulatum (fig. 68), and Annularia fertilis (fig. 69). 
The general character of the invertebrate fauna coincides with that of 
the transition; nearly the same families and genera occur, although the 
species are mostly specifically distinct. 
In the lower group of the carboniferous system, the mountain limestone, 
entire strata are filled with crinoidal joints, belonging principally to 
Rhodocrinites verus (fig. 70, a, b), and to Cupressocrinus crassus (fig. 71, 
a,b). Were and there are found pelvic fragments of Platycrinus levis 
(pl. 42, fig. 41), Actinocrinus triginta-digitalis (fig. 42), and a form nearly 
allied to the crinoidea, Pentremites ellipticus (fig. 48). These strata have 
consequently received the name of encrinital or entrochital limestone. The 
principal mollusca are Pleurorhynchus minor (pl. 42, fig. 44), Spirifer 
striata (fig. 46), Producta punctata (fig. 47), Terebratula acuminata 
(fig. 56), Bellerophon bisulcus (fig. 50), a Pleurotomaria (fig. 51), 
Euomphalus pentangulatus (fig. 52): of Cephalopoda, Orthocera breynia 
(fig. 45), Ammonites listeri (fig. 48), Ammonites striatus (fig. 49) ; of 
corals, Syringopora geniculata (fig. 53), and Favosites capillaris (fig. 54) ; 
of trilobites, Asaphus gemmuliferus (fig. 55). 
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