Echinoidea. 



II 



by 



Th. Mortensen. 



As in the Iiitroduction to Part I of the Ingolf -Echinoidea I have the agreeable dut\- to tender 

 my best thanks to several CoUeagues, who have assisted nie by sending material or otherwise. 

 I beg to offer m\ sincerest thanks to Dr. F. A. Rat her, Professor F. Jeffr. Bell, Prof. C. Chuu, Prof. 

 L. Doderlein, Dr. R. Fourtau, Prof. L. Joubin, Prof. R. Koehler, Dr. J. Lambert, Prof. 

 H. Lndwig, Prof. E. \". Marenzeller, Dr. J. CH. de !\Ieijere, Dr. M. Meissner, Prof. G. Pfeffer, 

 Prof. R. Rathbun, Miss M. J. Rathbun, Prof. Hj. Théel, Prof. A. E. Verrill, Prof. M. Weber. I 

 am especialh' 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. — Oi material importance for my stud\- of the irregiilar Echinoids have been repeated 

 visits to the British Museum, where Professor F~. Jeffr. Bell witli his usual great liberalit>" ga\'e me 

 access to the e.xtremeh' iinportant collection of Echinoidea from the Challenger -E.xpedition as well 

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

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

 North American Museums in wliich 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 extremeh- important collections in the Museum of Comparative Zoology at Harvard 

 College; but, fortunateh-, I found in the U. S. National Museum, where I niet the greatest liberalit>- 

 from Prof es.sor R. R a t h b u n and Miss M.J. Rathbun, almost all the types which I wanted especially 

 to study; and the stud\- 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, Yale College, where Professor A. E. \' er ri 11 most liberally gave me access to the whole 

 collection of the Museum. 



Copenhagen, February 1907. 



The Author. 



The Ingolt-Expedition. IV. 2. 



