KIDSTOX: THE FLORA OF THE CARBONIFEROUS PERIOD. 195 
Dactylotheca Zeiller. This is characterised by the ovoid-pointed 
sporangia, which are placed singly on the veins and open by 
a longitudinal cleft (Plate XXXI., fig. 3). The barren pinnules 
vary greatly in form, being entire, lobed, or crenate, according 
to the position they hold on the frond. On the main rachis, 
at the point of insertion of the pinnse, are curious, much-divided 
outgrowths, called aphlebia (Plate XXXL, fig. 2). These were 
originally supposed to be a climbing fern (Schizopteris adnascens 
L. & H.) which had used the frond of Dactylotheca as a sup- 
port. These aphlebia are an integral part of tlie frond on which 
they occur, and are found on other species of ferns belonging to 
various genera. 
Another Pecopterid genus, Mariopteris Zeiller, is extremely 
common in the Lower and Middle Coal Measures, but very rare 
in the Upper Coal Measures. The fructification is unknown, 
but the fern is distinguished by a double bifurcation of the 
rachis of the primary pinnae. The leathery texture of the pin- 
nules, difficult to describe but easily learnt from an examination 
of specimens, as w^ell as the nervation, appears to me to add 
a character to the genus, which I would be inclined to restrict 
for Mariopteris (^Pecopteris) muricata. Schl. sp. (Plate XXXIL, 
figs. 1 and la) and one or two close allies, but from which 
I would exclude such species as Sphenopteris latijolia Brongt. 
The double bifurcation of the primary pinnse, which occurs 
in this species, does not alone seem to me to be of much 
systematic importance. 
ALETHOPTERIDE.E. 
The Alethopteridece are closely related to the Pecopteridece, 
but the pinnules are generally obliquely placed on the rachis, 
the prominent mid-rib joins the rachis near the upper margin 
of the pinnule, and thus gives a somewhat decurrent character 
to the mode of their insertion on the rachis. The lateral 
dichotomously divided veins are very numerous and run to the 
margin at almost right angles with the mid-rib. The common 
Alethopteris lonchitica Schl. sp. well illustrates these characters 
(Plate XXXIL, figs. 2 and 3). 
