98 A HISTORY OF RECENT CRUSTACEA 
afferent opening on either side, by their powerful move- 
ments bring it back to the branchial cavity. ‘The two 
ridges on the maxillipeds, which are often densely fringed 
with hairs, meet in front and form a triangular break- 
water which prevents the streams intended for the bran- 
chiee from entering the mouth-opening. 
Of the rock-haunting species of the genera Plaqusia, 
Latreille, 1806, and Goniopsis, de Haan, 1835, Krauss 
speaks with a sort of admiration. At low tide they come 
bustling out of their crannies in ho-ts. By help of their 
soft elastic bodies, and their hmbs cut out for the very 
purpose, they clamber over rough blocks and steep sides 
of rock, jump from one crag to another, and creep into 
the most inaccessible crevices. They are not very swift, 
but very canny, so that on their own ground, in spite of 
their multitude, it is almost impossible to catch any of 
them. In the fear of pursuit they will let themselves drop 
several feet from one ledge on to another, or plunge a 
fathom down into the sea and paddle off to the nearest 
rock. Acanthdpus clavimanus, de Haan, is a tiny species 
nearly allied to Plagusia, but with different habits. It 
lurks under stones, and it may seem a light matter to turn 
over a stone and catch it, but before the stone is well over 
the crab will have whisked to the other side, and when at 
length it has been pinned fast, it is no easy task to drag 
away its thin body and clinging talon-like claws without 
breaking them. The name of this genus having been pre- 
occupied, it has been changed by Miers to Leieléphus. 
Plagusia contains species that come from the Atlantic 
and Pacific, and some of these have been taken in the Medi- 
terranean under circumstances worthy of note. In the 
winter of 1875 an iron vessel entered the port of Mar- 
seilles. It had come from Pondichéry, by way of the Cape 
of Good Hope, having had a long and stormy voyage in 
the most rigorous season of the year. To the iron plates 
of this ship had become attached a little forest of algze and 
barnacles; and living among these were a number of 
higher Crustacea of exotic origin. Two of the specimens 
were found by Professor Catta to belong to a new species 
