E c h i n o i d e a. 



II 



Th. Mortensen. 



As ill the Introduction to Part I of the Ingolf;-Echinoidea I have the agreeable dulv to tender 

 my best thanks to several Colleagues, who have assisted me b\- sending material or otherwise. 

 I beg to offer my sincerest thanks to Dr. F. A. Bather. Professor F. Jeffr. Hell, Prof. C. Chun, I'rof. 

 L. Doderlein, Dr. R. Fonrtau, Prof. L. Joubin, Prof. R. Koeliler, Dr. J. Lambert, Prof. 

 H. Ludwig, Prof. E. v. Marenzeller, Dr. J. C. H. de Meijere, Dr. M. Meissner, Prof. G. Pfeffer, 

 Prof. R. Rath bun. Miss M. J. Rathbuu, Prof. Hj. Theel, Prof. A. K. Verrill, Prof. M. Weber. I 

 am especially indebted to Professor Doderlein for sending me the proof sheets of his great work on 

 the Echinoidea of the German Deep-Sea Expedition and thus enabling me to use this work, before it 

 was published. — Of material importance for m\- studx of the irregular Echinoids ha\e been repeated 

 visits to the British Museum, where Professor F. Jeffr. Bell with his usual great liberalit\' ga\e nie 

 access to the extremeh important collection of Echinoidea from the Challenger -Expedition as well 

 as the other extensive collections of Echinoids in this Museum. F'urther, it was of the highest impor- 

 tance for me that I was, through the liberal grant of the Carlsberg F^und, enabled to visit those 

 North American Museums in which more considerable collections of Echinoidea are preserved. It was, 

 of course, rather a great disappointment for me that I could not get permission to make an\ studies 

 of the large and extremeh- important collections in the Museum of Comparati\e Zoolog\ at Harvard 

 College; but, fortunately, I found in the U. S. National Museum, where I met the greatest liberalitx 

 from Professor R. R a t h b u u and Miss M. J. Rathbun, almost all the t\pes which I wanted especialh 

 to stud\ ; and the study of the rich collections from the Albatross preserved there also gave many 

 important results. Likewise I had occasion to make several important observations in the Peabod\' 

 Museum, Yale College, where Professor A. E. \'errill most liberalh ga\e me acce.ss to the whole 

 collection of the Museum. 



Copenhaijen, February 1907. 



The Author. 



The In(;alf-Expedition. IV'. 



