Guide to the Crustacea, Arachnida, Onychophora and Myriopoda exhibited in the Department of Zoology, British Museum (Natural History) .. . nnules. Thesixth pair of abdominal appendages (uropods) are generally absent,rarely present as rudiments. Ihe third pair of maxillipeds are pan- of )lding doors generally broad and flattened, formingwhich cover the other mouth-parts. The Brachyura are usually divided into live Tribes, which,however, are not all of equal value : — Tribe 1— Dromiacea. Tribe 3—Oxyrhyueha. ,, 2 Oxystomata. ,, 4 Tribe 5 -Calonietopa. Decapoda—Brachyura, Cra6s. 65
Guide to the Crustacea, Arachnida, Onychophora and Myriopoda exhibited in the Department of Zoology, British Museum (Natural History) .. . nnules. Thesixth pair of abdominal appendages (uropods) are generally absent,rarely present as rudiments. Ihe third pair of maxillipeds are pan- of )lding doors generally broad and flattened, formingwhich cover the other mouth-parts. The Brachyura are usually divided into live Tribes, which,however, are not all of equal value : — Tribe 1— Dromiacea. Tribe 3—Oxyrhyueha. ,, 2 Oxystomata. ,, 4 Tribe 5 -Calonietopa. Decapoda—Brachyura, Cra6s. 65 The DiiOiMiACKA or Spouge-Crabs are tlie most primitive of the Tablu-caseexisting Brachyura. The last pair, or the last two pairs, of legs aredorsal in position, with hooked or prehensile claws, and are usedfor holding a piece of sponge, an Ascidian, or half of a bivalveshell, under which the animal is completely hidden. The mouth-frame is square. The primitive character of the group is shownespecially l:)y the retention of a vestigial pair of limbs on the firstabdominal somite of the female, and often on the sixth abdominal. Dnnnia rulgnris. Front view of a specimen canying on its back a mass of thesponge Clionc celata (reduced). [Table-case No. somite in both sexes {sec the exhibited specimen of Dromia laioi).The basal segment of the antenna is large and unusually free,the pits into which the antennules fold are not separated from theorbits, and the gills are, in most cases, more numerous than in theother Brachyura. The oviducts of the female open on the firstsegment of the third pair of legs. Many of the Dromiacea, especially the more primitive forms,inhabit the deep sea. Dromia vulgaris (Fig. 44), which occurs offthe South of England, belongs to the family Dromiidae, in whichthe last two pairs of legs are generally reduced in size, and are F (36 Guide to Cnisfacea. Table-case elevated on the l)ack. One of the specimens exhibited, taken intlie Bristol Channel, c
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectcrustacea, bookyear19
