The large tripinnate fronds are characterised by the long linear- or oval-lanceolate pinnules ([fig. 373])[1548] with a pointed apex and numerous bristle-like hairs on the lamina; two much smaller Cyclopteroid segments occur at the base of the pinnae which are terminated by the linear leaflets ([fig. 354], F, p. 535).
Neuropteris Scheuchzeri is characteristic of the Upper and Middle Coal-Measures of Britain and is recorded from several localities in North America and the Continent. Zalessky[1549] has recently recorded the species from the Coal-Measures of Donetz. The frequent occurrence of detached pinnules points to a caducous habit. Even single leaflets can, however, be identified by their large size, the pointed apex, and hairy lamina. The hairs are preserved as fine oblique lines simulating veins; they were so described by Roemer[1550] who took them for cross-connexions between the secondary veins and referred the pinnules to Gutbier’s genus Dictyopteris.
Another example of Neuropteris with hairy pinnules is described from the Commentry Coal-field by Renault and Zeiller as N. horrida[1551]. The oval-linear, bluntly rounded, pinnules are characterised by a median band of hairs on each surface and a narrower strip at the edge of the lamina.
Cyclopteris.
This generic name was created by Brongniart in 1828[1552] for specimens which he believed to be complete single leaves of orbicular or reniform shape similar to those of Trichomanes reniforme. The lamina is traversed by numerous dichotomously branched veins which spread from the centre of the base.
It was suspected by Lindley and Hutton[1553] that certain Cyclopteris leaves belonged to the frond of a species of Neuropteris, and some years later Lesquereux[1554] concluded that Brongniart’s genus was founded on orbicular leaflets of Neuropteris. In 1869 Roehl[1555] figured a specimen of Neuropteris bearing Cyclopteroid pinnules on its rachis. It is now universally admitted that Cyclopteris is not a distinct genus and that the specimens so named were borne as modified pinnules on the main rachis of Neuropteris and Odontopteris. It is, however, convenient to retain the name for detached leaflets which cannot be referred to the fronds on which they were borne. A specimen found by Mr Hemingway in the Upper Coal-Measures of Yorkshire and described in 1888[1556] affords a striking example of the large size attained by what was probably a frond of Neuropteris. The piece of main rachis reached a length of over 120 cm. and bore five pairs of Cyclopteris pinnules, some of which were 7 cm. long and 5 cm. broad. The complete frond must have reached a length of at least 4 metres. Fig. 370 shows some typical Cyclopteroid leaflets on the petiole of a Neuropteris frond.
Linopteris.
The Upper Palaeozoic fronds included in this genus are more familiar as species of Dictyopteris. Potonié[1557] has, however, pointed out that the creation of this name by Lamouroux in 1809 for a genus of Brown Algae which is still retained, makes it advisable to fall back upon the designation Linopteris. Gutbier[1558] proposed the genus Dictyopteris in 1835: Linopteris was first used by Presl[1559] in 1838. The fronds so named are identical with species of Neuropteris except in the anastomosis of the secondary veins; Linopteris bears to Neuropteris the same relation as Lonchopteris bears to Alethopteris. As in Neuropteris, Cyclopteroid pinnules occur on the petioles of Linopteris, but the veins form a fine reticulum. Grand’Eury[1560] records the association of Linopteris Brongniarti with seeds belonging to the genus Hexagonocarpon, a fact which points to the Pteridosperm nature of the foliage.
Some fertile pinnules of Linopteris Schutzei (Roemer) are described by Zeiller[1561] from Autun as bearing on the under surface of the lamina two rows of long and pointed sporangia, probably united in groups. The presumption is that these are microsporangia.
Fig. 374 is a reproduction of a careful drawing, originally published by Zeiller[1562], of a pinnule of the type-specimen of Gutbier’s species Linopteris neuropteroides. This species differs from Linopteris obliqua, instituted by Bunbury[1563] for specimens obtained by Lyell[1564] from the Coal-Measures of Nova Scotia, in the smaller size of the meshes. Linopteris obliqua occurs in the Upper and Middle Coal-Measures of Britain; it is recorded by Zeiller from Asia Minor, by Lesquereux[1565] from Pennsylvania, and by other authors from several European localities. The pinnules frequently occur detached from the frond and like those of some species of Neuropteris were caducous. Linopteris is rare in British strata.