It forms a crescent around the next section, the abdomen. The margin between the two forms a hinge that closes inward to protect the underside of the body when the crab is alarmed. The abdomen possesses 6 pair of spines along the margin which further protect the underside. A line of small indentations run along the median of the abdomen in pairs and represent attachment points for muscles which control the movement of the gills. The telson is not used for defense and, aside from being hard and pointed, is not dangerous.
Many people pick individuals up by their telson.
The underside of the crab carapace is taken up by five pairs of walking legs and the chelicera. The first segment of the walkings legs is called the coxae and in the first four sets of legs these are modified with large bristly spines used for feeding. The coxa in the fifth pair or legs bear a short spatula-shaped paddle which is used for cleaning the gills. The fifth pair of legs also contains several leaflike entensions which the crab uses for pushing and clearing mud and silt when it burrows.