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 of 
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.’ 
Thus in the lusitanian province Mr. McAndrew 
dredged off the coast of Galicia and Asturias, 212 
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 per 
cent. to Britain (chiefly celtic province). The shells 
common to the two or three provinces were chiefly 
those dredged from considerable depths. The littoral 
forms had amuch more distinct aspect. The mollusca 
of the ‘Porcupine’ expedition have not yet been 
thoroughly worked out. ‘They are in the hands of 
Mr. Gwyn Jeffreys, and his preliminary reports give a 
most interesting forecast of what we may expect when 
his labour is completed. He announces something 
like 250 new species. Some of the more interesting 
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 limited 
in number, and have already been examined by the 
writer with some care. The general distribution of 
the Echinodermata is not so well 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 
' Woodward, loc. cit. p, 362. 
