This tribe is included by some authors in the Anomura, and held to be closely related to the Galatheidea, but the unreduced abdomen is carried straight and unflexed, and gives a very Macrurous appearance to the animal. The Anomurous characters are the frequent reduction or absence of the antennal scale, the fact that only the first two pairs of pereiopods are ever chelate, and the reduced series of gills. The body is symmetrical, but the first pair of chelae is always highly asymmetrical. The posterior pairs of pereiopods, although small, are not characteristically reduced as in the Anomura. The animals belonging to this Tribe attain two or three inches in length, and generally burrow in sand or mud either in the littoral zone or in deeper waters; at the same time they can swim with considerable activity by means of the pleopods. =Fam. Callianassidae.=—_Callianassa subterranea_ is common at Naples, _Gebia littoralis_ in the North Sea. =Sub-Order 2. Anomura= In this division are included the so-called Hermit-lobsters and Hermit-crabs, in which the condition of the abdomen is roughly intermediate between that of the Macrura and that of the Brachyura. It is not much reduced in size, and the pleopods of the sixth pair are fairly well developed, but it is usually carried flexed towards the thorax, and is never a powerful locomotory organ as in the Macrura. The antennal scale, if present at all, is a mere spine, not the large leaf-like structure of the Macrura; and there is never a partition between the two first antennae as in the Brachyura. The last or last two pairs of pereiopods are reduced, and are turned on to the dorsal surface or carried inside the branchial chamber; but this curious character is met with again in certain Brachyura (Dromiacea and Oxystomata). =Tribe 1. Galatheidea.=[140] [Illustration: FIG. 114.—Dorsal view of _Munidopsis hamata_, × ½. (From an original figure prepared for Professor Weldon.) ] These are symmetrical crabs with a long carapace; the abdomen, which is as broad as the carapace, is always carried flexed under the thorax, and the sixth pair of pleopods are expanded to form with the telson a fan-like tail. The most anterior pereiopods are always much elongated and chelate; while the last pair are much reduced, and either turned up on to the dorsal surface, or else carried in the branchial chamber. The exact meaning of this last characteristic in these forms is doubtful; some of the species are said to carry shells temporarily upon their backs, a proceeding probably assisted by the last pair of thoracic limbs, while in others their limbs may be used for cleaning out the branchial chamber. Most of the Galatheidea, for instance, the common _Porcellana_ and _Galathea_, are littoral animals, and may be found hiding under stones and in crevices on the shore; but a number occur in deep water, e.g. _Munida_ and _Munidopsis_. [Illustration: