Abstract
A LTHOUGH the Holothuridea show a greater tendency to a bilateral arrangement of their internal organs than any other group of the Echinodermata, most of them are fusiform or cylindrical in shape, and the radiate symmetry prevails so far externally that the five radial ambulacral vessels and their appendages are similar, that they run symmetrically at equal distances from one another from the oral to the apical pole, and that they are used indifferently for the purposes of progression. In all Holothuridea, however, two ambulacra, those of the bivium, are essentially dorsal, while the three ambulacra of the trivium are ventral; and in one little group of the ordinary Dendrochirota, which includes the well-known genus Psolus, a very distinct ambulatory tract is defined on the ventral surface of the body, and the pedicels of the rest of the ambulacral system are either absent or greatly modified. From the form of the ambulatory disk and the position of the mouth and apex, a Cuvieria, with its tentacles expanded, has a very striking resemblance to a large Doris.
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THOMSON, C. The Elasmopoda (Hjalmar Theel) a New order of Holothuridea . Nature 21, 470–473 (1880). https://doi.org/10.1038/021470a0
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DOI: https://doi.org/10.1038/021470a0