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Show 258 MR. E. A. SMITH ON T H E MOLLUSCA [May 6, Thyone 8T + 2*. Pseudocucumis lOT-f \Qt. Thyonidium 10T+ 10*. Amphicyclus 14 (T + T ) 4-1 Ot. Actinocucumis 16 to 18(T + T')4-2£. Orcula .• 10 to 15(T4-T')-|-5*. Phyllophorus 12 to \6(T + T') +5 to 6t\ I have tried, in the phylogenetic table which I append, to combine with the approved mode of presenting hypotheses the objective method used so successfully by Prof. Huxley in some of his later communications to this Society. At the side I mark the stages of 10T, 8T + 2t, and 10T4-10*; along the middle rise the stichopod forms, to the left those that are more or less heavily armed, and to the right the strictly sporadiform forms. A n inspection of this table shows that the forms are now seen to he too closely and intimately allied to allow of the sharp differentiation into three groups which was suggested by Prof. Semper. If, however, we have lost an artificial scheme, we have perhaps got one step nearer to a clear perception of the genetic relationship of the genera of the Dendrochirotae ; and, after all, it is better for us to recognize the tangled web and woof of the animal kingdom than, in these days, to be content with definitions overloaded with exceptions, or distinguishing marks that tell us nothing of the past, and give us but uncertain aid in the present. The day of linear classifications is gone. 3. A n Account of the L a n d and Freshwater Mollusca collected during the Voyage of the ' Challenger' from December 1872 to May 1876. By E D G A R A. SMITH. [Received April 4, 1884.] (Plates XXII. & XXIII.) The object of the voyage of the 'Challenger' having been " to investigate scientifically the physical conditions and natural history of the deep sea all over the world," it is not surprising that the number of terrestrial and fluviatile Mollusca brought home by the Expedition is comparatively small. Evidently no real attempt was made at collecting, but only such species appear to have been picked up as presented themselves to members of the scientific staff when on shore at the various localities. The whole collection comprises only 152 species, some of which, however, possess considerable interest, and several are new to science. The following Report has been drawn up in as brief a manner as 1 Echinocucumis would apparently have the formula of 8*"-|-2T, and is possibly a slightly degraded form ; I have omitted it from the phylum. |
