SMART AND COOKE : MARINE SHELLS OF SCILLY. 287 



The comparatively southern latitude of these islands is 

 illustrated by the extreme scarcity of such shells as Buccimim 

 undatum, Fusus gracilis, F. antiqutis, and Littorina littorea. 



Dredging at Scilly is not altogether an easy matter, con- 

 sidering the available appliances. Roughly speaking, the work 

 is done on ground of the following nature : — The channels 

 which separate the larger islands from one another are shallow, 

 some, as St. Martin's Flats, being left almost bare at low water 

 of spring tides ; others, as Crow Sound, being about 8 — lo fms. 

 deep, with a bottom of muddy sand. Outside the islands the 

 water deepens almost immediately, sinking rapidly to about 

 40 — 50 fms., which is in fact a portion of the sea bottom, 

 always within the 100 fm. line, which extends in every direction 

 outside the South British Channels until the edge is reached of 

 the great Atlantic depths. 



The bottom alternates from rough gravel to shelly sand, 

 with stones here and there, but is on the whole very uniform 

 in character, and in the shells it produces. The best ground, 

 as will be seen from the list which follows, is outside the rock 

 known as Menavawr, about half a mile to two miles N. to NE., 

 in about 35 — 40 fathoms. But as this ground is practically in 

 the open Atlantic, it is not by any means possible always to 

 work it, as a very little wind raises sea enough to prevent the 

 dredge keeping the bottom at such a depth, while even if there 

 is no wind there will frequently be enough ground sea to pro- 

 duce a similar or more fatal result. Nearly all our deep sea 

 work was done outside Menavawr, and no doubt if the ground 

 more to the southward of the islands were dredged systematic- 

 ally, several new species might be added to the hst. 



It will be seen therefore that this list has no pretensions to 

 completeness, but simply represents what may be done by a 

 very limited amount of dredging, combined with (on the part 

 of one of us) tolerably close shore hunting for about four years. 



