THE BA.SALTS OF IRELAND AND SCOTLAND. 663 



G-oniopteris stibiaca, Unger, sp. (Plate XXVI. fig. 8.) 



Eocene basalts, Lough Neagh. 



The only British locality for this species prior to its discovery 

 at Lough Neagh was Bovey Tracey. It seems to have been 

 local, but not uncommon there. All the frouds found were 

 destitute of sori ; but Prof. Heer considered it to be identical 

 with a large species from the Aquitanian of Monod in Switzerland, 

 whose fronds he estimated to have been 3 feet in length and a 

 foot wide. Prom these he supplemented his diagnosis, and fixed 

 the size, form, and position of the sori. If the identification is 

 correct, several other supposed species should also be united 

 with it, such as Lastrcea helvetica and L. dalmatica. It is also 

 given an Arctic range by Heer ; but there seems, from the de- 

 scription, some little doubt as to the identity of the Greenland 

 species with ours. A very considerable difference in the vena- 

 tion of pinnules from different parts of the same frond might be 

 looked for in a species of such large dimensions, and the minute 

 apex of a pinnule from Lough Neagh, when magnified, has a 

 quite different aspect, and is almost exactly like G. Bunburii in 

 its venation. While, however, considerable latitude would be 

 permissible as to the extremes of venation and cutting that might 

 safely be associated in one species, when the specimens are all 

 from the same locality and bed, the large number of existing 

 genera (e. g. Acrostichum and Nephrodium) in which pinnae of 

 this type occur should make us anxious to note even the most 

 inconsiderable persistent differences. Thus a fern found by the 

 Marquis de Saporta in the gypsum of Aix, Provence, appears at 

 first glance completely identical with it ; but it differs in reality 

 in an important particular, the anastomosis of the inferior veinlets 

 of the segment not being continued up to contact with the pair 

 above. This peculiarity removes it from the group G.prolifera, 

 Mett., of Tropical America, to which our British specimens 

 seem very closely allied, and associates it with G. crenata, Mett., 

 also of Central America and the Antilles. I may here mention 

 a slight peculiarity in the Lough-JNeagh specimen, which is, that 

 instead of the veinlets of contiguous segments anastomosing 

 regularly in pairs, the lower veinlet on one side, in at least some 

 instances, anastomoses with three in succession on the other. 

 Want of recognition of even so slight a character as that on which 

 Saporta insists might lead to very erroneous views as to the 

 former distribution of a species. G. stiriaca seems to have been 



