180 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
The results of a trip of this sort are very largely dependent upon 
the assistance of others, and I have an unusually large number of 
courtesies to acknowledge. To my colleagues in the Division of 
Geology at Harvard University I am deeply indebted for making the 
expedition possible. To Prof. Charles Schuchert I owe much for 
advice, and for letters of introduction over a route which he had 
himself travelled. Mr. I. P. Tolmacev, Curator-in-chief of the Mu- 
seum of the Imperial Academy of Science in Petrograd, made arrange- 
ments and secured letters which greatly facilitated our work in Russia. 
It was he, and the excellent assistant, Mr. Carl Lackschewitz, whom 
he secured to travel with us, who enabled us to work continuously and 
comfortably during our stay in Russia. Mr. Lackschewitz, a grand- 
son of the celebrated Middendorf, and grand-nephew of Fr. Schmidt, 
in whose footsteps we were following, proved our invaluable interpreter, 
advisor, and business agent. To the knowledge and skill of Mr. O. 
Knyrko preparator at the Museum in Petrograd, I am indebted for 
much beautifully preserved material collected during the ten days in 
which he acted as guide in the region south of Lake Ladoga. To the 
many other gentlemen who assisted us in Russia, some of whom are 
named in the introduction to Dr. Twenhofel’s report, I also wish to 
express my thanks. 
Just as I write these acknowledgements comes the sad news of the 
death of Professor Dr. Johan Christian Moberg, but for whose kindly 
assistance my visit to Sweden would have been of little value. Cutting 
short his own field season, Professor Moberg devoted himself for 
almost three weeks to guiding me over the Cambrian and Silurian 
deposits of Scania. Without his intimate knowledge of the extremely 
restricted outcrops in this region, my work would have been fruitless, 
indeed, impossible in the restless moments of the first weeks of the war. 
In Norway we were greatly indebted for guidance and hospitality 
to Professor Kiaer and Dr. Holtedahl who made possible a great deal 
of work and collecting jn a very short time. Nor must I omit an ex- 
pression of my obligation to M. Pierre Pruvost of Lille for escorting 
me during three pleasant days spent among the Palaeozoic outcrops 
of the Ardennes. It is with more than usual feeling that I make 
these expressions of sincere gratitude to those who assisted me, 
especially as there is only too much cause to fear that they may never 
see these lines. 
Finally, I wish to express my appreciation of Dr. Twenhofel’s 
kindness in undertaking his part of the work, and of his hearty 
codperation in the field. 
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