The arthropods in general were provided with a carapace; most of them were crustaceans.
At least three segments of the trunk are left uncovered by the carapace.
The last four or five segments of the trunk are free from the carapace.
The Monosphrida comprise all those Sphroidea in which the carapace is represented only by one single lattice-shell.
In Chelonia the ribs are generally combined with the carapace.
It is also found on the carapace of crabs and Limulus, and on mollusks.
In these animals the body is compressed and the carapace is not hard.
The antenn are plume-like and about as long as the carapace.
The eye-stalks are long and fit into sockets on the carapace.
The surface of the carapace and limbs is more or less granulated.