Echinoidea. 



I. 



By 



Th. Mortensen. 



The present work forms the first part of a planned revision comprising all the arctic Echinoderms, 

 excepting the Holothurioidea. The basis of the work is formed by the rich material of the 

 Ingolf-Expedition together with the large collections of arctic Echinoderms found at our Zoological 

 Museum from earlier expeditions. To the arctic fauna all the species are referred which are found in 

 the Norwegian Sea, the Greenland Sea, the Denmark Strait, and at the coast of West-Greenland, as 

 also in the White Sea and the Polar Sea with the Bering Strait. Of forms that are only found south 

 of the large ridge between Greenland and Iceland, and between Iceland and the Faroe Islands, only- 

 such as have been taken by the Ingolf-Expedition, have been included in the work. 



During the examination of the material the absolute necessity of taking into consideration also 

 other more or less nearly related forms soon made itself felt By and by I became aware of the fact 

 that the classification hitherto used with regard to the families treated of here, was quite erroneous, 

 and so I have sought to include into the examination as many forms as possible in order to be able 

 to give the new classification that had to be made, so broad a base as possible. Inspector G. M. R. 

 Levins en placed the whole rich collection of Echinoids of the museum at my disposal with the 

 greatest readiness; but as far from all species and genera are represented in this collection, I have 

 applied to several foreign naturalists, and have everywhere been met with the most obliging kindness 

 and friendliness, so that I have been enabled to examine almost all known genera and species com- 

 prised in the groups treated of here. 



The following gentlemen have sent me Echinoids on loan or in exchange: Dr. Appellof 

 (the Museum of Bergen), Prof. F. Jeffr. Bell (British Museum), Prof. E. v. Beneden (Liege), Prof. 

 Collett (Christiania), Prof. Doderlein (Strassburg), Conservator J. Grieg (the Museum of Bergen), 

 Prof. Koehler (Lyons), Prof. P. de Loriol (Geneve), Prof. E. v. Marenzeller (Vienna), Geh.rath, 

 Prof. E. v. Martens (Berlin), Geh.rath, Prof. K. M obi us (Berlin), Prof. Monticelli (Naples), Prof. P. 

 Pallary (Oran), Prof. G. Pfeffer (Hamburg), Prof. R. Rathbun (U. S. National Museum), Prof. 



The Inijolf-Expedition. IV. i. I 



