This species, described by Schlotheim in 1820 as Filicites lonchiticus and previously figured by Scheuchzer[1574], is abundant in the Middle and Lower Coal-Measures of Britain[1575]. It is characterised by large tripinnate fronds, probably quadripinnate in the lower part, bearing primary pinnae of a more or less triangular form divided into pinnate branches replaced in the apical region by linear segments. The pinnules, 8–30 mm. long and 3–5 broad, are linear- or oval-lanceolate with an obtuse apex; the upper margin of the lamina is slightly contracted at the base, while the lower edge is decurrent.
Fig. 375. Alethopteris Serlii (Brongn.). From a specimen in the York Museum. ¾ nat. size.
Alethopteris Serlii (Brongniart)[1576]. Fig. 375.
This species, figured by Parkinson in 1811, closely resembles A. lonchitica, but is distinguished by the more crowded and relatively longer pinnules which are joined to one another by a narrow connecting lamina (Fig. 375). The secondary veins in A. Serlii are rather finer and more numerous. Grand’Eury[1577] records the association of the seed Pachytesta with fronds of this species in the Coal-Measures of St Étienne.
A. Serlii is very abundant in the Upper Coal-Measures but rare in the Middle Coal-Measures of Britain[1578].
Lonchopteris.
This name was proposed by Brongniart[1579] for sterile fronds from Upper Carboniferous rocks which are practically identical with species of Alethopteris, but differ in the reticulate venation of the pinnules. It has been pointed out in a previous chapter[1580] that Lonchopteris is usually used for Palaeozoic species, the Wealden leaves, which were placed in this genus by Brongniart, being transferred to Weichselia.
There can be little doubt as to the close relationship of Lonchopteris with Alethopteris: both may be referred to the Pteridosperms. Lonchopteris rugosa Brongn.[1581] ([fig. 290], B, p. 399) and L. Bricei Brongn., both British species, are fairly common in Upper Carboniferous strata. In L. rugosa, a Middle Coal-Measures species, the anastomosing secondary veins form polygonal meshes ([fig. 290], B, p. 399) smaller than those of L. Bricei.