132 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [NoV. 29, 



mens from the Tarentaise, and I must add that I received the kindest 

 assistance from Professor Sismonda and his brother, who afforded me 

 every possible facility for a full and satisfactory investigation. The 

 detailed descriptions of the species will be found at the end of this 

 paper. But I must observe in the first place that I found very con- 

 siderable difficulty in arriving at any satisfactory conclusions. The 

 portions of plants contained in these Alpine slates, though very nume- 

 rous, are in general very imperfect ; they are crowded and jumbled 

 together in great confusion, often much crushed and distorted ; they 

 are almost always converted into, or coated with, a silver-white talc, 

 which, while it gives them a beautiful appearance, is not very favour- 

 able to the preservation of the more minute and delicate markings ; 

 and, in particular, the details of the venation, on which the determi- 

 nation of fossil ferns so much depends, are seldom well exhibited. 

 Above all, the fronds of the ferns are very often distorted in a most 

 singular manner, whether in consequence of drifting, or of a process 

 of crystallization, perhaps accompanying the upheaval of the slates. 

 This distortion causes the leaflets, not only in different parts of the 

 same frond, but even on opposite sides of the same pinna, to differ 

 widely both in apparent form and in direction, so that it is often ex- 

 ceedingly difficult to determine what was their original and normal 

 character. Under these circumstances it will not be thought surpri- 

 sing that I should speak with a certain degree of caution and hesita- 

 tion as to the specific identity of most of these plants. 



The results of my examination may be thus stated. Among the 

 specimens preserved in the museum at Turin I was able to distinguish 

 only fourteen different forms, for I will not venture to call them spe- 

 cies. Of these nine are Ferns, two Calamites, and three Astero- 

 phyllites or AnnularicE. Two of the Ferns, namely Odontopteris 

 Brardii and I'ecopteris Cyathea, may be pronounced with tolerable 

 certainty to be identical with characteristic and well-knowTi plants of 

 the coal-measures. Three, or perhaps four others have a strong re- 

 semblance to coal-measure plants, with which they may very probably 

 be specifically identical, but I cannot feel certain of them. Another 

 seems to be a remarkable and hitherto unnoticed variety of Odonto- 

 pteris Brardii, connecting that species with O. obtusa of Brongniart. 

 The eighth is perhaps a new species, but its nearest allies are plants 

 of the coal formation. Of the ninth the specimens are too imperfect 

 to admit of determination. Of the remaining plants Calamites ap- 

 proximatus and Annularia longifolia appear to be absolutely identical 

 with coal-measure plants ; and the other two Annularice or Astero- 

 phyllites are at least very similar to carboniferous forms. The other 

 Calamite is undeterminable. 



I now proceed to the fossil plants of the Col de Balme and other 

 localities near Chamounix. Sir Henry De la Beche was, I believe, 

 the first to record* the occurrence of impressions of ferns in the 

 schistose rocks of the Col de Balme, and he noticed their close resem- 

 blance to those of the coal formation. These impressions have since 

 become well known, and are familiar to most visitors to Chamounix, 



* In 1819. 



