662 ME. J. 6TAEKIE GABDNEE OS EOCENE FEEffS FEOM 



Goniopteeis Bunbueii, Seer. (Plate XXVI. fig. 9.) 



Eocene basalts, Lough Neagb. 



This should be credited witb a far wider range in the European 

 Tertiaries than has previously been extended to it ; but it is a 

 type apparently rare, if not unknown prior to the Middle Eocene 

 period. Though it comes very near in venation and outline to 

 Goniopteris diver sifolium and G. tetragonumivom. Brazil, the per- 

 sistent absence of any traces of sori in all of the numerous spe- 

 cimens that I, as well as others, have come across, suggests that it 

 would be better placed in some genus in which the fertile fronds 

 are separate. One fulfilling these conditions and bearing an other- 

 wise strong resemblance to it is Onoclea orientalis ; but this differs 

 in possessing free veinlets. The genus Onoclea is practically re- 

 presented only by three existing species, forming respectively the 

 subgenera JEuonoclea and Struthiopteris, the former with copi- 

 ously anastomosing, and the latter with free veinlets. In Onoclea 

 germanica the segments are cut down, and the veinlets look as if 

 they must unite but for this ; but in some forms of the closely 

 related O. orientalis the pinnules have merely waved margins, 

 yet the veinlets never anastomose. Some principle or repulsion 

 keeps them from contact, however nearly they may approach ; yet 

 it is quite certain that a common ancestor must at some period 

 have united the two very distinct existing types ; and the vena- 

 tion we are dealing with must almost of necessity have been one 

 of the links. Genera have their rise and fall, and such a large 

 proportion of the fossil plants I have. already examined belong to 

 genera poorly represented now, that I am predisposed to search 

 among such for survivals of the floras of Eocene age. 



The case stands thus :— As far as outline and venation go, our 

 fern might be placed in Goniopteris, JSTephrodium, Diplazium, 

 Polybotrya, or other genera. These in a living state are sepa- 

 rable by their sori. The fossils are destitute of any trace of sari. 

 True, they are fragmentary, and have been floated down by water, 

 and the sori might therefore have been so completely rubbed oil' 

 as to leave no trace. The balance of probability is against this ; 

 for it is not uncommon for sori to be preserved on ferns asso- 

 ciated with them in the very same deposits. The determination 

 must thus be based on a nice appreciation of probabilities, and 

 may rest on an accumulation of data which separately would be 

 trivial and valueless. It was described as Lastrasa by Heer. 



