4 (JO THK DEPTHS OF THE SEJ. [CHAP. ix. 



while one family type, the Echinothuridce, has been 

 hitherto only known in a fossil state, the entire 

 group find nearer allies in the extinct faunae of the 

 chalk or of the earlier tertiaries than in that of 

 the present period. 



As I have already said, the mollusca procured 

 during the three years' dredging are in the hands 

 of Mr. Gwyn Jeffreys for identification and descrip- 

 tion. Prom the large number of new species, and 

 from the complicated relations which many of the 

 forms from deep water bear to species now widely 

 separated from them in space, or belonging to past 

 geological periods, the task will be a difficult one, 

 and we cannot expect its completion for some time 

 to come. In the meanwhile, Mr. Gwyn Jeffreys 

 has published several preliminary sketches which 

 are full of promise that his complete results will 

 be of the highest interest. 



Mr. Gwyn Jeffreys believes that the deep-water 

 mollusca which were dredged throughout the whole of 

 the area examined from the P&roe Islands to the coast 

 of Spain, are almost all of northern origin. Most of 

 the species which have been already described were 

 previously known from the Scandinavian seas, and 

 many of the undescribed species belong to northern 

 genera. He points out that the molluscan fauna 

 of the Arctic Sea is as yet almost unknown ; but he 

 reasons from the large collections made at Spitz- 

 bergen by Professor Torell, and from the fact that 

 fragments of mollusca have been brought up in 

 many deep-sea soundings within the Arctic circle, 

 that the fauna is probably varied arid rich. He 

 instances soundings taken in 1868 by the Swedish 



