216 MR ROBERT KIDSTON ON 



PL II. fig. 7. 



From Monckton Main Colliery, near Barnsley, Yorkshire. Horizon. — Barnsley 

 Thick Coal. Middle Coal Measures. 



The specimen shows portion of a primary (?) pinna, and the fragment preserved is 

 26 cm. long. The rachis at its thickest part is about 7 cm. broad. 



At certain parts of the rachis the little rough points are almost entirely effaced — 

 probably from pressure — which, at other portions, are distinctly preserved, and this 

 shows how much the absence or presence of such characters depends on the condition of 

 preservation. 



The plant is the Sphenopteris crenata, L. and H., but is not so well preserved, as far 

 as the lateral pinnae are concerned, as those shown at figs. 5 and 13. The specimen is 

 a fruiting one, of which only a portion is shown natural size. It is similar to the fossil 

 given at fig. 13. The upper ultimate pinnae (not shown in the figure) are barren, and 

 bear simple pinnules, of which some have simple and others bifurcated veins, identical 

 with those shown at fig. la, fig. 45, and fig. 13a, and which are typical Filicites plumosus. 

 It is, therefore, seen that under certain conditions, when the sporangia are copiously 

 produced, it results in the limb of the pinnules being more or less reduced. In the case 

 of fig. 5, and in certain of the pinnae of figs. 7 and 13, the reduction of the limb has 

 reduced the pinnules to narrow teeth-like lobes, leaving only that portion of the limb 

 on which the sporangia themselves are placed. This example also shows very beauti- 

 fully the Aphlebia (originally supposed by Lindley and Hutton to be a parasite, and 

 named by them Schizopteris adnascens), arising from the rachis at the points where 

 the pinnae are given off. 



Mons. Zeiller has shown,* from specimens collected at Larche, that the Aphlebia 

 which occur on the rachis are disposed in pairs at the origin of the Aphlebia bearing 

 pinnae, — one on the anterior, and the other on the posterior face of the rachis. They 

 may thus be compared to two wing-like structures that arise from the back and front of 

 the rachis, and bending upwards and outwards embrace the base of the pinna they 

 subtend between them. 



The Aphlebia are bipinnately divided into sharp-pointed lanceolate segments. 



Zeiller has observed a similar arrangement of the Aphlebia on Diplothmema Zeilleri, 

 Stur.t 



PI. II. fig. 6. 



From the same Locality and Horizon as the last. 



This fossil shows an early state of development of several pinnae, — what might be 

 called the " Spirorbis " condition of the plant, — where the pinnae are still spirally coiled. 

 The Aphlebia, however, appear to be fully developed, and therefore probably acted as 

 protective organs to the more tender and immature portions of the frond. 



* Bassin houil. et perm, de Brive., p. 26, pi. ii. figs. 3-4. 

 t Flore f oss. Bassin hovil. d. Valenciennes, pi. xvi. fig. 1. 



