40 THE DEPTHS OF THE SEA. [CHAP. i. 



in which dredging has been attempted at any consider- 

 able depth, say 30 or 40 fathoms, that the number oi 

 species common to the province dredged and to the 

 province to the north of it, is greatly increased 

 by the investigation being carried into a deeper zone. 1 

 Thus in the lusitanian province Mr. McAndrei 

 dredged off the coast of Galicia and Asturias, 21! 

 species, 50 per cent, of which were common to the 

 coast of Norway; and off the south of Spain 335 

 species were obtained, of which 28 per cent, were 

 common to Norway (boreal province), and 51 pei 

 cent, to Britain (chiefly Celtic province). The .shells 

 common to the two or three provinces were chiefl; 

 those dredged from considerable depths. The litton 

 forms had a much more distinct aspect. The mollus< 

 of the f Porcupine ' expedition have not yet beei 

 thoroughly worked out. They are in the hands oi 

 Mr. Gwyn Jeffreys, and his preliminary reports give 

 most interesting forecast of what we may expect wh< 

 his labour is completed. He announces somethii 

 like 250 new species. Some of the more interestii 

 of these, and the general phenomena of their distri- 

 bution, will be referred to in a future chapter. 



The echinoderms of the expedition are more limil 

 in number, and have already been examined by the 

 writer with some care. The general distribution of 

 the Echinodermata is not so w r ell known as that of the 

 Mollusca, There are many littoral and sub-littoral 

 species. Many of these are local, but many have a 

 wide geographical distribution, usually along what 

 Edward Forbes calls a ' homoiozoic belt/ a belt of 

 nearly similar circumstances of climate extending 

 1 Woodward, loc. cit. p. 362. 



