i68 



CRUSTACEA EUCARIDA DECAPODA 



CHAP. 



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. 1 



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 sixtli 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 re- 

 duced, and either turned up 

 on to the dorsal surface, or 

 else carried in the branchial 

 chamber. The exact mean- 

 ing of this last characteristic 

 in these forms is doubtful; 

 some of the species are said 

 to carry shells temporarily 

 upon their backs, a proceed- 

 ing 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 



1 Milne Edwards and Bouvier, Ann. Sci. Nut. (7), xvi., 1894, p. 91. 



FIG. 114. Dorsal view of Munidopsis hunmtn . 

 x A. (From an original figure prepared 

 for Professor Weldon.) 



