The investigations of which I now publish an account, deal not merely with the scanty stock 

 of Ceriantharia collected on the Ingolf Expedition, but with all northern species that I have received 

 for investigation, chiefly from the museum of Copenhagen, the museum of Trondhjem and the natural 

 history museum (Riksmuseum) at Stockholm. As the number of known Ceriantharia from the northern 

 seas, even including the species I have described, is comparatively small, I have preferred not to 

 scatter my account of these few species over two or possibly more publications, because a view 

 as connected as possible of the morphology of the Ceriantharia, in the way set forth below, seems 

 to be not without value, especially as this account is based on close study of a comparatively laro-e 

 number of species (see below) and in many points deviates considerably from the accounts previously 

 published, such as v. Ben ed en's and Mc Murrich's. Through the kind courtesy of the editors of 

 the scientific results of the Ingolf Expedition, I have been put in a position to publish my investi- 

 gations in the reports of the Ingolf Expedition. For this I must express my gratitude, and at the same 

 time I have to thank the heads of the respective departments of the museums whose collections I 

 have used, above all Dr. Levins en of Copenhagen, Professor Theel of Stockholm, Professor A ppel- 

 lof of Upsala formerly of Bergen, Dr. Svenander formerly of Trondhjem, and Dr. Broch of Trond- 

 hjem. On morphological grounds chiefly I have also taken account in the present work of C. amer- 

 icanus, though this species is found more in the soiith. The specimens of this species described are 

 partly from the museum of Copenhagen, partly from Beaufort-station in North Carolina, the director 

 of which. Dr. All er, has sent me some specimens preserved in formalin, a kindness for which I tender 

 my warmest thanks. 



Simultaneously with this work I am publishing in Mittheilungen a. der zoologischen Station zu 

 Neapel a paper describing the morpholog\- of a larval form and a few adult forms of Ceriantharia 

 already known. As account is taken of tliese forms also in the synopsis of the morphology (4th 

 section), I would request any reader who takes a special interest in the structure of the Ceriantharia, 

 to pay special attention to that work also. 



I subdivide this paper into the following four parts. 



(i) A brief introduction comprising the literature of the subject, the geographical distribution, 

 and a survey of the Ceriantharia of the north. 



(2) An account of the different species. 



(3) The classification of the Ceriantharia. 



(4) Concerning the morphology of the Ceriantharia. 



Tlie Danish Inoolf-Expcditinn V. j. 



