STYLASTERIDAE 



23 



A very speaking example of how little attention has been paid to the Atlantic Stylasteridae 

 on reference being made to the fannistic conditions of this ocean is fonnd in a statement in Parker 

 and Has well's Textbook of Zoology (1897 p. 147): The Hydrocorallinae occur only in the tropical 

 portions of the Pacific and Indian Oceans, where they are found on the coral reefs < partly or entirely 

 surrounding many of the islands in those seas . Nevertheless, some of the oldest, quite identifiable 

 descriptions of Stylasteridae are those given by Gunnerus in his work Om nogle norske 

 Coraller« (1768). His figures leave no doubt as to the identity of the species and his originals, which 

 all came from the west coast of Norway, are preserved in the Zoological Museum of Trondhjem. — 

 The work of Gunnerus has been little known owing to the humble and little distributed journal 

 in which the paper was published. But several papers have also been published later in which the 

 Atlantic Stylasteridae are mentioned and here we must place in the first rank Pour tales' excellent 

 work on the deep-sea corals (1871), in which he describes quite a number of Stylasterids from the 

 American side of the Atlantic, especially from the waters round Florida. Pour tales described here 

 for the first time Pliobotlirns syiiniirtricns and also mentions a second of the North Atlantic species. 

 Sty/aster rosetes, under the name of Stylaster enthcsctin: In addition, we have still two other, old 

 records from the North Atlantic. G. O. Sars (1871) has given a classic description of the living Allopora 

 norvegica and P. j\I. Duncan (1874) mentions Stylasterids from the P'aeroe Channel. With exception 

 of the work of Gunnerus all these papers are cited in detail by Moseley (1881) in his great work 

 on the Stylasteridae of the >-■ Challenger . 



Later information regarding the northern Stylasterids is \-ery meagre. Storm (1882) mentions 

 Stylaster gemmascens and Allopora norvegica from the Trondhjem F'jord; there is a casual remark by 

 Hickson (1891), that he has had material of Allopora oculiiia from the Hardanger Fjord and of 

 Allopora norvegica from the »Triton;< Expedition; lastly, J.A.Thomson (1910) informs us, that he 

 has examined colonies of Stylaster from Rockall. 



On the basis of the literature, therefore, we cannot penetrate very far into the biogeographical 

 conditions of the northern Stylasterids. In this respect the comparatively large material collected by 

 the »Ingolf <, »Thor « and the East Greenland Expedition of 1900 fills up a large gap in oui knowledge. 

 Supplementing this material with that preserved in the museums of Christiania and Trondhjem and 

 further with observations from the Trondhjem Fjord we are able to throw a fairly good light on the 

 biogeographical conditions of this enigmatical group in our northern waters. 



As already- noted, the Stylasteridae in the Norwegian Sea are typical coral reef dwellers. 

 Yet at places in the Trondhjem Fjord Stylaster gemviasceiis is able to live in somewhat shallower 

 water, sometimes even in towards a depth of 50 metres. This must depend on the sj^ecial biophysical 

 conditions of the fjord and it is of interest to note in this connection, that according to the investigations 

 the species is only able to live in the shallower parts at places where projecting, submarine cliffs or 

 barriers force the masses of water upwards which are brought in b>- the tidal wave. The shallowest 

 occurrence of the species lies near its innermost boundary in the fjord. In the outer parts of the fjord, 

 on the other hand, where the sides of the fjord are steeper and more regular, the species as also 

 Stylaster [Allopora) norvegicns is bound to the Lophohelia reefs and both species here as elsewhere 



