LOWER COASTAL ANIMALS 



125 



The large New Zealand scallop 

 (Pecten medius) is found in 

 the lower reaches of the shore 

 ooze. Manikua Harbour, New 

 Zealand. 



winkles are characteristic of rocks and stones, but are absent from sand 

 and mud. But in mangrove swamps tree roots and trunks protrude and 

 form a firm foundation on which animals can maintain themselves, and 

 in mangrove swamps everywhere we found these snails on the projecting 

 roots and lowermost branches. They were different species from those on 

 the shores, but they were periwinkles, and they lived like other members 

 of their family. Thus we see that two requirements of periwinkles are a 

 firm foundation and adequate spindrift. 



As pointed out by the Danish zoologist C. G. J. Petersen ( i860 — 1928), 

 it is a different set of animals which live on the loose bed from the ones 

 which inhabit the firm parts that lie scattered about it, such as stones, 

 dead shells, etc. Petersen distinguished between what he called the "in- 

 fauna", belonging to the actual sea-bed or associated with its loose surface, 

 and the "epifauna", which must have firm objects to which it can attach 

 itself, at least in the early stages of growth. Periwinkles are thus epifauna, 

 the creatures which live in the mud of the mangrove swamp being infauna. 



On the Galathea we were often glad of an admixture of epifauna in 

 our hauls from the soft bottom. Since a dredge is liable to get damaged 

 in attempts to work it on submarine rocks and reefs, whether these are in 

 shallow or deep water, we were usually afraid of fishing there. But we 



