598 R. KIDSTON ON SOME CARBONIFEROUS FERNS. 
Hymenophyllites guadridactylites has not, so far as I am aware, 
been yet discovered in Britain. 
In concluding these somewhat lengthy notes, I have only to 
express the hope that those who have the opportunity of collecting 
fossil plants, will avail themselves of it, as at present our knowledge 
of the British fossil flora is very imperfect. 
EXPLANATION OF PLATE XXV. 
Zeileria delicatula, Sternberg, sp. 
Fig. 1. Two pinne, mostly barren, but showing places from which sporangia 
have fallen, which were indicated on the fossil as darker points. 
2. Portion of frond, showing the fruit in an early state of development. 
They occur here as closed globular involucres. 
3. Portion of another frond, bearing barren and fructifying pinnules mixed 
with each other on the same pinne. 
4, Small portion of a barren frond. 
5. A small specimen, showing the opened indusia. 
5a. A split indusium, showing the four segments: enlarged. 
6. A few open indusia. 
6a. The same enlarged, showing the valves into which the indusia split. 
7, 8. Small specimens, showing mature and split indusia. 
9. Barren pinna. The form named var. trifida, Gopp. 
9a. The same, enlarged. 
10. Small specimen, showing the split indusia. 
11,12. A few indusia supported on their elongated pedicels. 
12a. The same, enlarged. 
Discussion. 
Mr. Carrutners remarked that the discovery of fructification 
in fossil ferns was of great importance, the characters presented 
by the fronds in both recent and fossil forms being so similar. 
Generic distinctions to be of value must be founded mainly upon 
the fructification, and without it the classification was to some 
extent mere guesswork. He said that he had formed rather diffe- 
rent opinions from the author on some of the points referred to, 
but the subject required much caution. Calymmatotheca was pro- 
bably a Hymenophyllaceous fern, like Cyclopteris hibernica. About 
Zeilleria and Urnatopteris it was more difficult to decide. 
Dr. Mvriz congratulated the author upon the interesting nature 
of his communication. 
Mr. Kinston, in reply, pointed out the distinction between the . 
sporangia of the different forms referred to in the paper, and said 
that he was sure, if Mr. Carruthers would examine the specimens, 
he would recognize the importance of these distinctions. 
