INTRODUCTION. 



To the courtesy and kindness of General G. von Helmersen, of St. Petersburg, I am 

 indebted for the means of studying the minute fossils of the white Carboniferous 

 limestones of the neighbourhood of Moscow and elsewhere in Russia, the Foraminifera of 

 which formed the subject of the researches of Fischer von Waldheim, Rouillier and 

 Vosinsky, Ehrcnberg, and d'Eichwald ; and Dr. Herrman Abich, of Tiflis, in Georgia, has 

 placed me under the like obligation for rock-specimens of similar age from the Caucasus. 



To Dr. F. B. Meek, of Washington, Dr. C. A. White, late State-Geologist of Iowa, 

 Professor II. L. Smith, of Geneva, New York, and Dr. S. B. Buckley, State-Geologist 

 of Texas, I am beholden for similar attentions in respect to the Carboniferous strata of the 

 United States. 



With so large an accumulation of material, the question arose whether the whole 

 ' subject of the Carboniferous Foraminfera might not be treated in a single paper, and, 

 having gone through the minuter forms, my attention was naturally turned to the 

 important group, not represented at all in our British fossiliferous rocks, constituting the 

 genus Fidsulhia. I found, however, before I had proceeded far in this direction, that my 

 friend Dr. Guido Stache, of Vienna, was already at work upon the genus in its geological 

 relations ; and it became evident that the zoological and structural details which had 

 been in part worked out might with advantage be withheld for the moment, and the 

 history of this generic type, in its extensive and varied aspects, reserved for a separate 

 paper at some future time. 



The intimate natural relationship which subsists between the limited Rhizopod-fauna 

 of the Permian formations and the more extensive one of the Carboniferous epoch has 

 necessitated their collateral study ; and as this has resulted in some additions to the 

 knowledge of the former group, and considerable revision of its nomenclature, the history 

 of the two is presented, as it has been worked out, in one series. To the friendly 

 co-operation of Dr. R. Richter, of Saalfeld, in a variety of ways, any completeness which 

 the portions referring to the Thuringian Zechstein may possess is due. 



Thus it has come -about that what was originally projected as a Monograph of 

 British Carboniferous Foraminifera only, has become the more comprehensive treatise, 

 geographically and geologically, indicated by its present title. 



One word more to finish personal matters. In the authorship of many previous 

 papers, Professor W. K. Parker, F.R.S., and Professor T. Rupert Jones, F.R.S., have 

 been my colleagues. Whilst my attention has been occupied with these investigations 

 they have been engaged in other departments of science. None the less have I had the 

 advantage of discussing with them questions of difficulty as they have arisen, and if their 

 names do not appear very frequently in the following pages, it is only because I prefer 

 to make this more general acknowledgment. After all, the present work is little 

 more than a continuation of research on the lines which they laid down originally, 

 and which we have so long followed in company ; and their general approval of the 

 conclusions it embodies is perhaps its best letter of introduction. 



