Echinoidea. 



II 



Th. Mortensen, 



As in the Introduction to Part I of the Ingolf -Echinoidea I have the agreeable duty to tender 

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

 I beg to offer my sincerest thanks to "Dr. F. A. Bather, Professor F. Jeffr. Bell, Prof. C. Chun, Prof. 

 L. D cider lei n, Dr. R. Fourtau, Prof. L. Joubin, Prof. R. Koehler, 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. Rath bun, Prof. Hj. Theel, Prof. A. E. Verrill, Prof. M. Weber. I 

 am especially indebted to Professor Doderleiu 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 my study of the irregular Echinoids have been repeated 

 visits to the British Museum, where Professor F. Jeffr. Bell with his usual great liberality gave me 

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

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

 tance for me that I was, through the liberal grant of the Carlsberg Fund, 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 any studies 

 of the large and extremely important collections in the Museum of Comparative Zoology at Harvard 

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

 from Professor R. Rath bun and Miss M. J. Rathbun, almost all the types which I wanted especiallv 

 to study; 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 Peabody 

 Museum, Vale College, where Professor A. E. Verrill most liberally gave me access to the whole 

 collection of the Museum. 



Copenhagen, February 1907. 



The Author. 



The In^oIf-ExpedTtton. IV. 





Vt. 



