Trilobites

Benthonic (in bed)

Lives on the sea or river floor, in or on top of the sediment

Epifaunal

Lives on top of the sediment

Pelagic (lethargic)

Floats in the water column

Nektonic (neck deep in the water)

Actively swims in the water column

Infaunal (in the sea bed)

Lives in the sediment, perhaps a burrower

Front appendage

Detect environment and feeding

Antenna

Detect environment, part of the sensory system

Glabella

Part of the cephalon formed of the stomach

Compound eye

Made up of calcite plates for vision. Part of the sensory system

Free cheek

Part of the cephalon that breaks away from the skeleton during ecdysis

Facial suture

Line of weakness where the exoskeleton breaks first during ecdysis

Fixed cheek

Part of cephalon which remains attached to the exoskeleton at the beginning of ecdysis

Genal angle

Part of cephalon which may have spines attached

Thoracic segment

One thoracic segment, made up of three articulating plates

Pleuron

Segment adjoining the axis

Pygidium

Fused tail piece which may have spines. May stabilise the animal

Axis

Central lobe running down the length of the trilobite exoskeleton

Back appendages

Walking or swimming legs