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. ^Tt. 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, ISIr. Carl Lackschewitz, whom 

 he secured to travel with us, who enabled us to work continuouslv 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. Twenliofel'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. \Yithout 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 in 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 

 co5peration in the field. 



