THE FOSSIL FLORA OF THE YORKSHIRE COAL FIELD. 219 



This example shows the arrangement of the sporangia on the pinnules. In this 

 specimen the pinnules are oblong, obtuse, and entire, and placed close to each other. 

 The nervation is obscure, but apparently the lateral veins have bifurcated, and each arm 

 has borne a sporangium (figs. 9a and 9b). On these smaller pinnules the sporangia 

 occupy the whole space between the midrib of the pinnule and its margin, and were 

 parallel with the course of the lateral veinlets — in fact, were placed on them. 



The sporangia are oval, but the apex is slightly more pointed than the base. They 

 measure about 60 mm. long. Their walls are composed of elongated coriaceous cells 

 without any indication of an annulus. Fig. 9c shows a sporangium magnified 25 

 times. 



PI. II. figs. 8 and 8a. 



From the same Locality and Horizon as the last. 



This small specimen shows the barren condition of the form usually associated with 

 the name of Pecopteris dentata, Brongt. , and is similar to that given by Zeiller in his 

 Flore foss. Bassin houil. d. Valenciennes., pi. xxvi. fig. 1. The basal inferior pinnule 

 is small and lobed, and occupies the angle formed by the union of the rachis with the 

 parent stem. The superior basal pinnule is, on the other hand, the largest on the pinna. 

 The nervation is not well shown, and seems to be immersed in the tissue of the pinnule. 

 The rachis is rough. 



Specimens from Cooper's Colliery, Worsborough, near Barnsley, Yorkshire. 

 Horizon. — Barnsley Thick Coal. Middle Coal Measures (Reg. Nos. 2093-2100). 



These specimens occur on a light grey coloured shale, but are not so well preserved 

 as those already described. They exhibit a slightly larger form of the plant, and the 

 sporangia are slightly longer and proportionally narrower than those shown in my figures. 

 They are not, however, so sharply pointed as those given by Zeiller in the original 

 description of his genus Dactylotheca. It was upon these differences that I presumed 

 that Pecopteris plumosa might be specifically distinct from Pecopteris dentata, but 

 I have since seen that what I thought might prove a distinguishing character does not 

 hold, as these slight variations in the size and form of the sporangia appear to depend 

 on the position of the pinnules and pinnae on the frond on which the sporangia 

 occur. 



Distribution in Britain. 



Dactylotheca plumosa occurs in the Upper, Middle, and Lower Coal Measures. It 

 attained its maximum period of development in the Upper Coal Measures, and though less 

 frequent in the Middle Coal Measures it is still comparatively common. In the Lower 

 Coal Measures, however, it has all but disappeared, and from this division I only know of 

 four specimens, two of which are those figured by Lindley and Hutton, — one as Sphenop- 



vol. xxxviii. part ii. (no. 5). 2 G 



