72 



(Cyclopieris) the nerves of which radiate from the base. From 



the Yorkshire coalfield. Slightly reduced. 



ALETHOPTERIS. 



The large compound fronds of Alethopteris have oblong leaflets, 

 which are usually longer than broad, and attached to the axis by 

 their entire base. The base of the leaflet often runs downward to 

 join on to the leaflet below. There is a central or median nerve, 

 which extends to the apex of the leaflet, and lateral nerves are 

 usually given off almost at right angles to the median nerve. They 

 may be simple or forked. 



Page 40. Alethopteris lonchitica (Schlotheim).* Part of a 

 very common frond, showing the shape of the leaflets, and the nerv- 

 ation. The median nerve lies in a well-marked groove. From the 

 Nottinghamshire coalfield. Slightly enlarged. 



Page 41. Alethopteris Serli (Brongniart).* Another species 

 differing in the shape of the leaflets, and in the details of the 

 lateral nervation. From the Somerset coalfield. Slightly reduced. 



Page 42. Trigonocarpus sp. The complete seed of an A lethop- 

 teris. The seed had a thick, fleshy outer coat, which is well seen in the 

 photograph, forming the broad border of the specimen. The central 

 oval portion, partly white in colour, which extends upwards as a 

 long spout, is an impression of the inner, hard seed coat, enclosing 

 the seed itself. From the Nottinghamshire coalfield. X 2. 



Page 43. Trigonocarpus Parkinsoni, Brongniart.* Casts 

 of the seed cavity. The outer and inner seed coats and the seed 

 itself, see page 42, have often perished completely, and all that 

 remains is a sandstone cast of the seed cavity. This has three 

 prominent ridges ; hence the name Trigonocarpus . From the South 

 Lancashire coalfield. Natural size. 



PECOPTERIS. 



The fronds oi Pecopteris were large and much branched, the leaflets 

 being undivided, often oblong in shape, and the two margins fre- 

 quently parallel. They were attached by their whole base to the 

 axis. The apex of the leaflet is usually blunt. There is a well- 

 marked, central or median nerve, froni which other lateral, simple 

 or forked nerves spring at a wide angle. 



Plate 44. Pecopteris arborescens (Schlotheim).* A typical 

 species with very regular, oblong leaflets, rounded at the apex. Each 

 leaflet has a median nerve, with simple, unbranched lateral nerves. 

 From the Somerset coalfield. Slightly reduced. 



Plate 45. Pecopteris oreopteridia (Schlotheim).* Another 

 species in which the lateral nerves fork. From the Somerset 

 coalfield. Natural size. 



Plate 46. Pecopteris polymorpha, Brongniart.* In this 

 species many of the lateral nerves fork twice. From the Somerset 

 coalfield. ^ natural size. 



Plate 47. Pecopteris Miltoni (Artis).* A very common species. 

 From the Somerset coalfield. Slightly enlarged. 



Plate 48. Pecopteris plumosa (Artis).* In this species the 

 leaflets are triangular and pointed. The ix\xzX\^Q.2X\on{^Dactylothecd) 

 is known. From the Somerset coalfield. X |, 



