470 



PEOFESSOE G. J. ALLMAN ON THE HTDEOIDA 



brought up from the enormous depth of 2435 fathoms. These evidences of abyssal hydroid 

 life have never come into my hands : they appear to have been lost ; so that a nearer 

 determination of them is now impossible^ 



The cold area lying between Shetland and the Faroe Isles, where the bottom is over- 

 flowed by a deep icy current from the Polar Seas, and whose discovery by the ' Porcupine ' 

 explorers constitutes one of the most important additions to our knowledge of the physical 

 geography of the North Atlantic, is not without a deep-sea Hydroid fauna, although its 

 bottom varies from the freezing-point of fresh water to nearly two and a half degrees of 

 Fahrenheit below it. The two new species of jT/Mwar/a already alluded to were obtained 

 from it where the temperature of the bottom was as low as 30° Fahr. ; while, from the 

 same area, the new Plumularian genus {Cladncarpus), with the new species of Diphasia 

 and Lafoea, also referred to above, were obtained from water whose temperature varied 

 in different places from 30°-5 Fahr. to 29°-8 Fahr. 



It will thus be apparent that, so far as the natural history of the Hydeoida alone is 

 concerned, the results of the expedition are important, bringing, as they do, to our 

 knowledge many species hitherto unknown, and throwing new light on the relations 

 between this most interesting group of organisms and the physical conditions which 

 surround them. 



The following species, already known and described in systematic works, were obtained 

 during the expedition of 1869: — 



' See Preliminary Report, Proc. Eoy. Soc. vol. xviii. 1869, p. 429. 



