Anomuran crabs, including squat lobsters, do not use the last pair of legs
for locomotion and, in life, these may not be visible so that the animals
appear to have only three pairs of walking legs, in addition to the chelae.
Hermit crabs and lobsters are easily recognised as such and mud shrimps can
be usually separated from true shrimps and prawns by the combined features
of large chelay (pincers), a more or less dorso-ventrally flattened and
loosely articulated abdomen - and by their burrowing mode of life.

This new Synopsis-volume covers those Crustacea Decapoda not included in
earlier Synopses-volumes 15 (Coastal Shrimps & Prawns) and 25 (Shallow Water
Crabs), both still available!