THE PORCELAIN CRABS 171 
appendages to the fourth, to the fifth, and sometimes to the 
third segment. 
Notwithstanding the brachyuran characteristics this 
legion is found to be in close affinity with the next, the 
Galatheinea. Here it is supposed that the pleon has 
become reduced in size and has lost its importance as an 
organ of locomotion, owing to the special habits which 
the animals have adopted. They are found under stones 
between tide-marks and in shallow water among stones, 
sponges, and corals. One species has been taken at a 
depth of 390 fathoms. There is but one family. 
Family Porcellanide. 
The characters of the single family are those of 
the legion. Kleven genera are assigned to it, most of 
which were instituted by Stimpson in 1858, and some on 
very slender distinctions. Only one belongs to British 
waters. 
Porcellana, Lamarck, 1801, has the ‘front’ dentate, 
the first joint of the second antennee much produced, fully 
reaching the margin of the carapace. ‘The chelipeds 
have a projecting lobe near the base of the inner margin 
of the fifth joint, the terminal joint often contorted. The 
walking-legs have the terminal joint short and robust, 
ending in a single claw. ‘To this genus belong the only 
British species of the family, Porcellana platychéles (Pen- 
nant) and Porcellana longicornis (Linn.), both of which 
are common under stones, along which they slidder with 
some rapidity. They will sometimes flatten themselves 
against the upturned stone, remaining quiet and evidently 
trying to look as if they were not there. Quite after the 
fashion of their kindred, the Galatheidee, they will lift up 
their claws to resist attack, but their flattened habit of 
body makes this posture of defence in their case ridicu- 
lously ineffective. If one of the threatening claws be 
seized, they pretty readily relinquish it and skurry away. 
To understand the likeness between these crustaceans and 
the Galatheidz it is necessary to flatten out the pleon of 
