Body short, capable of contraction into a sphere, smooth, convex.
Abdomen with about 8 articulations, without any dorsal longitudinal furrows.
Buckler sub-lunate, with large lateral eyes.
Tail expanded, not so large as the buckler, without lobes.
Genus Eighth. Illænus.
Body ovate oblong, contractile.
Head rounded in front, eyes small, in the temples, very remote.
Abdomen with from 9 to 10 articulations, trilobate.
Tail expanded as large as the head.[8]
[8] Some of the species described by Professor Dalman as included in this genus, we think ought to be referred to that of the Isotelus.