Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0101clau Year: 1884 463 of biramous swimming feet, which from the three posterior free Moments of the tliorax. The thoracic legs are either, at least in part, biramous (with swimming ramus), or as in the Decapods the exopodite is absent and the legs have the form of ambulatory appendages. They then terminate with simple claws : the anterior frequently with large chehe. The terminal joints may however be broad plates, in which case they can be used as swimming feet. The biramous legs o
Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0101clau Year: 1884 463 of biramous swimming feet, which from the three posterior free Moments of the tliorax. The thoracic legs are either, at least in part, biramous (with swimming ramus), or as in the Decapods the exopodite is absent and the legs have the form of ambulatory appendages. They then terminate with simple claws : the anterior frequently with large chehe. The terminal joints may however be broad plates, in which case they can be used as swimming feet. The biramous legs of the sixth abdominal segment are. as a rule, broad and fin-like and form, together with the last abdominal segment which is transformed into a large plate (telson), the caudal fin. The feet of the five anterior abdominal segments, on the other hand, are sometimes swimming feet (Stomatopoda), sometimes serve to carry the eggs, or the anterior may assist in copulation (in the male). They may however be more or less rudimentary and some of them absent. With rare excep- tions (J///x/'/^) all the Thoracostraca po-->ess gilfe, which are either tufted or composed of regular lancet-shaped leaves. The gills are appen- dages of the liiub> ; in the Stomatopoda \'ii'. 363.—Cephalothorax of Agtacusfluviafilis, after removal they are attached to Of the branchiostegite (). K, Gills ; B, ros the abdominal feet in trum ; ° scaphognathite (of the second maxilla); Mxf', third maxilliped. the Sehizopoda and Decapoda to the maxillipeds and ambulatory feet. The Cumacea are without gills, except for a single pair on the second pair of maxil- lipeds. In the Decapods they are contained in a special branchial chamber beneath lateral expansions of the carapace (branchiostegite) (fig. 3G3). The organs of circulation also attain a high, degree of development, tin- highest not only among the Crustacea, but in general amongst all Arthropods. A heart and vessels are always present. In th
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