The life of crustacea / by W.T. Calman.

  • William Thomas Calman
Date:
1911
Catalogue details

Licence: In copyright

Credit: The life of crustacea / by W.T. Calman. Source: Wellcome Collection.

    75/392 page 45
    feet are all alike, and are flattened and leaf-like in form, resembling those of the Branchiopoda. The first four pairs of abdominal limbs are large two- branched swimming feet, but the last two pairs are reduced to small vestiges. Two of the most impor- tant points in which the Nebaliacea differ from all the other Malacostraca are that there are seven instead of six somites in the abdomen (the last somite has no appendages), and that the telson has connected with it a pair of movable rods forming a “ caudal fork ” like that of the Branchiopoda. On account of the leaf-like thoracic feet and the posses- sion of a caudal fork and other features, the Nebaliacea were formerly classified with the Branchiopoda, but a closer examination of their structure has shown that they are true Malacostraca. In having an additional somite in the abdomen and in other points, however, they may be regarded as forming a link between the Malacostraca and the lower forms of Crustacea, and for this reason they are set apart as a series Leptostraca, while the other orders form a series Eumalacostkaca. The orders of the Eumalacostraca, again, are grouped, as shown in the table of classification, into four divisions. The first of these, the Syncarida, includes only one order, comprising a few small Crustacea (see Fig. 84, p. 264) which have recently been discovered in fresh water in Tasmania and Australia. They have no carapace, and all the
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