464 REPORT — 1895. 



shore waters seems to bring out is that the classification of submarine 

 deposits into 'terrigenous' and 'pelagic,' which was one of the earliest 

 oceanographic results of the ' Challenger ' Expedition, and which is still 

 adhered to in the latest 'Challenger' volumes as an accepted classification, 

 does not adequately represent or express fully the facts. Terrigenous 

 deposits are supposed to be those formed round continents from the waste 

 of the land, and are stated to contain on the average 68 per cent, of silica. 

 Pelagic deposits are those formed in the open ocean from the shells and 

 other remains of animals and plants living on the surface of the sea above. 

 Ordinary coast sands and gravels and muds are undoubted terrirjenous 

 deposits. Globigerina and j-adiolarian oozes are typical pelagic deposits. 

 But in our dredgings in the Irish Sea, where the deposits ought all to be 

 purely terrigenous, we meet with several distinct varieties of bottom 

 which are not formed mostly from the waste of the land, and do not con- 

 tain anything like 08 per cent, of silica ; but, on the contrary, are formed 

 very largely of the remains of plants and animals, and may contain as 

 little as 23 per cent, of silica. Such are the nullipore bottoms, and the 

 shell sand and shell gravel met with in some places, and the sand formed of 

 comminuted spines and plates of echinoids which we have found off the 

 Calf Island. These deposits are really much more nearly allied in their 

 nature, and in respect of the kind of rock which they would probably 

 form if consolidated, to the calcareous oozes amongst pelagic deposits than 

 they are to terrigenous deposits, and yet they are formed on a continental 

 area close to land in shallow water. Moreover, although agreeing with the 

 pelagic deposits in being largely organic in origin, they differ in being 

 derived not from surface organisms, but from plants (the nullipores) and 

 animals which lived on the bottom. Consequently tlie division of deposits 

 into ' terrigenous ' and ' pelagic ' ought to be modified or replaced by the 

 following classification : — 



1. Terrigenoits (Murray's term) — where the deposit is formed chiefly of 



mineral particles derived from the waste of the land. 



2. Neritic'^ — where the deposit is chiefly of organic origin, and is 



derived from the shells and other hard parts of the 

 animals and plants living on the bottom. 



3. Planktonic (Murray's pelagic) — where the greater part of the 



deposit is formed of the I'emains of fi'ee-swimming 

 animals and plants which lived in the sea above the 

 deposit. 



Mr. Clement Reid, F.G.S., to whom the deposits are handed over for 

 detailed examination, reports as follows : — 



' The series of dredgings examined since the last report is most inter- 

 esting from a geological point of view. One is again struck by the common 

 occurrence of loose angular stones at places and depths apparently well 

 beyond the reach of any bottom drift — at least beyond the reach of 

 currents likely to move such coarse material. This stony sea-bed is in all 

 probability the result of submarine erosion of glacial deposits. Its occur- 

 rence renders comparison between recent marine deposits of these latitudes 

 and Tertiary deposits a task of peculiar difficulty ; for not only is the 

 nature of the true marine sediments masked, but the fauna also must be 



' Adopted from Haeckel's term for the zone of shallow water marine fauna 

 (see PlanMon-Studien, Jena, 1890; also Hickson's Fauna of Beev Sea, 1894). 



