FIG. 115.—Zoaea of _Porcellana_, × 20. _T_, Telson. (After Claus.) ] The shallow-water species have ordinarily developed eyes; the various species of _Munida_, which occur in fairly deep but by no means abyssal regions, have usually very large and highly pigmented eyes; while in _Munidopsis_, which is characteristic of very deep water, the eyes are degenerate and colourless, as shown in Fig. 114. The Zoaeae, or young larval stages of the Galatheidea, are characterised by the immense length of the spines upon the carapace (Fig. 115). The young Zoaea which hatches out from the egg resembles in other respects that of the Brachyura. The Metazoaea, however, differs from that of the Brachyura in the fact that the third maxillipede is first present as a biramous swimming organ, and at its first appearance is not developed in its definitive form. The other thoracic limbs are not schizopodous when they appear, and indeed in nearly all respects the development proceeds as in the Brachyura. =Fam. 1. Aegleidae.=—The gills are trichobranchiae, and there are eight arthrobranchs. There are no limbs on the second abdominal segment of the male. The abdomen is not carried folded on to the thorax. The first two characteristics separate this family from all the other Galatheidea. _Aeglea laevis_, a fresh-water species from the rivers of temperate S. America, is the sole representative. =Fam. 2. Galatheidae.=—The abdomen is not folded against the thorax. The members of this family are often littoral in habit (_Galathea_, Fig. 116), but often go down into great depths (_Munidopsis_, Fig. 114). [Illustration: FIG. 116.—Dorsal view of _Galathea strigosa_, × ½. (From an original figure prepared for Professor Weldon.) ] =Fam. 3. Porcellanidae.=—The abdomen is folded against the thorax, and the body has a crab-like form. These are always littoral in habit, never descending into the depths. _Pachycheles_ in the tropics, _Porcellana_ with numerous species in all seas, _P. platycheles_ being a common British species. =Tribe 2. Hippidea.= The Mole-crabs have the habit of burrowing in sand, and their limbs are peculiarly modified into digging organs for this purpose (see Fig. 117). In other respects they are seen to be closely related to the Galatheidea by the form of the carapace, the condition of the abdomen, and the reduced last thoracic limbs.