KIDSTOX: TIIK FLORA OF THE CARBONIFEROUS PKRIOD. 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 foi'iii, being entire, lobed, or crenate, according 

 to the position they hold on the frond. On the main rachis, 

 at tlie point of insertion of the pinme, are curious, much-divided 

 outgrowths, called aphlebia (Plate XXXI., fig. 2). These were 

 originally supposed to be a climbing fern (Schizopteris adnascens 

 L. ct H.) which had used the frond of Dactylotheca as a sup- 

 port. These aphlebia are an integi'al part of the 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, difiicult to describe but easily learnt from an examination 

 of specimens, as well as the nervation, appears to me to add 

 a chai'acter to the genus, which I would be inclined to restrict 

 for Mariojderis (Pecoptei'is) muricata, Schl. sp. (Plate XXXII. , 

 figs. 1 and la) and one or two close allies, but from which 

 I would exclude such species as Sphenopteris latifolia Brongt. 



The double liifurcation of the primary pinna;, which occurs 

 in this species, does not alone seem to me to be of much 

 systematic importance. 

 Alethopteride^. 



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 piimule, and thus gives a somewhat decurrent character 

 to the mode of their insertion on the I'acliis. 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). 



