1877. | 167 {Lesquereux. 
SPHENOPHYLLUM, Bret. 
Stem articulate, leaves verticillate, cuneiform, crenulate, dentate, or lobed 
at the upper part which is truncate or rounded; midrib none; nerves 
straight, diverging fan like, simple at the base, dichotomously forking once 
or twice. 
Here also, the vegetable fragments, which we refer, legitimately it seems, 
to this genus, differ in one point from the typical characters established 
from Carboniferous specimens. In these, the leaflet, generally four to 
six, are separated to the very base orfree. Inthe Silurian plants, the whorls 
or leaflets, four or five, compose a single leaf, the divisions being lobes, 
cut indeed to near the point of attachment to the stem, where they are 
joined in obtuse sinuses. The character is distinctly seen upon the speci- 
men fig. 4 and 5, enlarged in 4* and 5*. None of the authors describing 
this genus, since it was fixed by Brongniart, has remarked upon the connec- 
tion of the leaflets at their base, though this connection is often represented 
by the figures given of species of Sphenophyllum, as for example, S, 0b- 
longifolium, Germ. and Kaulf. in Geinitz, Verst. v. Sachsen, pl. xx, fig. 12, 
where a whorl is represented with six leaflets free from the stem, whose 
place is marked by a circular round central scar, the leaflets being united 
at their base as by a ring. I must say also, that in the very numerous 
specimens of Sphenophyllum which I have had for examination, I have 
very often remarked this connection of the leaflets, but never, however, as 
distinct and as distant from the base as in the following species. In ¥. 
Schlotheimii and S. oblongifolium, the nerves are positively simple at the 
base, though two or more in the same leaflet. This character of course 
implies a connection of the border of the leaflets at or near the base, and in 
this case, they do not leave distinct impressions of their point of attach- 
ment to the stems. I therefore admit the Silurian plants as truly referable 
to this genus, the difference remarked in its characters being merely specific 
and apparently proper to a type not yet fully developed. 
SPHENOPHYLLUM PRIM&VUM, Lesqx. 
Pl. T, figs.3-5. 
Stems or branches slender, articulations close, equidistant ; leaves in 
whorls of four or five leaflets connected towards the base and joined by 
slightly obtuse sinuses ; leaflets either truncate and crenulate at the top, or 
sometimes deeply split or lobate; nerves simple at the base, sparingly 
dichotomous, forking mostly once, even simple. 
If we would not take into account the connection of the leaflets, the rela- 
tion of this species to S. Schlotheimii, Bret., and especially to S. oblongi- 
folium, Germ., as figured by Geinitz (loc. cit.), would appear very close. 
The difference would be marked merely by the shorter leaflets or the 
smaller size of the plant and the less enlarged divisions. In the Carbon 
iferous species, which is also frequently found in the American coal meas 
ures, the veins, simple at the base, and generally two for each leaflet, have 
also few divisions, forking only once or twice. 
