55 
a. o. — as well as a Nemertean and various forms of Nematodes. 
Further the Amphipod Haustorius arenarius Slabber is very com- 
mon in such localities; it is quite exceptionally well adapted for 
digging in the sand, all its legs being much widened. Also an- 
other Amphipod, Synchelidium brevicarpum Båte has been found liv¬ 
ing in the same places. Two more Crustaceans are very common 
here, namely the Amphipod Bathyporeia Robertsoni Båte (a. o. spe¬ 
cies) and the Isopod Eurydice pulchra Leach. These two forms are 
preally freeswimming, but as they live mainly at the edge of the 
water, they are very often left on the beach by the retreating 
waves, and then they instantly disappear in the sand, both of 
them digging very swiftly. The dark spotted Eurydice swims al¬ 
most like a Gyrinus and often conceals itself in the patches of 
5cum of the more gently moving waves. — In places less exposed 
'to the surf also the Cumacean Cumopsis Goodsiri v. Ben. is found 
iving in the same way as Bathyporeia , and also Copepods (of the 
: amily Harpacticidæ). — Corystes cassivelaunus has not been found 
vithin the tidal zone on the Danish coasts, while it is known to 
)ccur there on the British coasts. 
In tropical regions a corresponding fauna has been observed, 
>nly much more conspicuous. Large Annelids (Eunicids) protrude 
vith their heads above the sand in the retreating waves, just as 
ioes Scolecolepis (— N. S. Wales, Panama); the Anomurous Crusta- 
:ean Elippa („sea cockroach“) lives in great numbers in the sand, 
vhere the waves wash up and down, catching dead fishes etc. 
hrown up by the waves and dragging them down into the sand 
o devour them there. Also a mussel, Donax , has its real home 
lere. It is most admirably adapted for living under such physical 
konditions, its siphons being perfectly covered by branched promi- 
lences from the margin, so that no sandgrains can pass through; 
ilso this form burrows very fast, thus avoiding being washed away 
)y the waves. Amphipods living in the same way as Bathyporeia 
lave likewise been observed in various places. 
In sheltered places we find the large, shallow flåts 
„Vader“) which are dry during ebb-tide and flooded during high 
ide, the depth generally being only some few centimeters; they 
ire thus never exposed to surf or waves of any noticeable size. 
^t the Danish coasts such flåts are found especially at the is- 
