208 MR ROBERT KIDSTON ON 



produced, it results in a partial reduction of the limb of the pinnule. Upper portion of 

 the fructifying pinnae barren. 



Rachis rough, with small points from which caducous scales have fallen. 



Remarks. — The fronds of Dactylotheca plumosa, Artis, sp., must have attained to a 

 large size. I possess a specimen from Radstock, showing portions of two primary (?) 

 pinnae, neither of which is complete, but the most perfect, though it neither shows base 

 nor apex, is about 16^ inches long, and has a width of 12 inches, though even here 

 the extremities of all the lateral pinnae are broken off. Its complete width could not 

 have been less than 18 inches, and was possibly greater. On fronds of this size the 

 pinnule cutting must have varied greatly according to the position held by the pinnules 

 on the frond. 



The figures which accompany this communication better illustrate the various forms 

 of pinnule cutting than could be conveyed by words. From simple pinnules, to others 

 divided into sharp tooth-like lobes, all intermediate forms occur, which graduate into 

 each other by insensible transitions. On some specimens, the simple undivided pinnule 

 is found associated with those divided into prominent saw-like teeth. 



To these polymorphous forms, many specific names have been given, and this is more 

 fully referred to in the description of the specimens figured on the plates. 



That these so-called species are only different portions of the same plant — and might 

 equally well be fragments of the same frond — will, I believe, be admitted by anyone who 

 has had the opportunity of examining such a large and fine series of specimens of 

 Dactylotheca plumosa, Artis, sp., which it has been my good fortune to meet with. 



These various forms cannot even consistently be described as varieties, for they only 

 represent different portions and conditions of development — barren and fruiting — of 

 the same frond ; but should it be thought desirable to distinguish the particular form 

 found at any given locality, it can easily be done by indicating the various forms, as 

 forma crenata, forma caudata, &c. 



Notes on Specimens figured by various Authors. 



Filicites plumosus, Artis. Antediluvian Phytology, p. 17, pi. xvii. 



Artis, like many of the older and, unfortunately, like some much more recent writers 

 on Fossil Botany, gives no enlarged drawings of the details of the pinnule cutting and 

 nervation of his Filicites plumosus, and his description is very meagre. Probably, this 

 has contributed to the imperfect maimer in which this fern is understood. Of the small 

 portion of the fruiting specimen shown on the upper left-hand corner of his plate, he says, 

 "Fructification near the margin of the leaflet." This appearance is only shown on im- 

 perfectly preserved specimens, of which I possess some similarly preserved from Cooper's 

 Colliery, Worsborough Dale, near Barnsley,* to the small fragment figured by Artis. 



* Collected by Mr W. Hemingway. (Reg. No. 2094, &c.) 



