258 MR. E. A. SMITH ON THE MOLLUSCA [May 6, 



Thyone 8T + 2^ 



Pseurlocncumis IOT4 1')^. 



T/njonidium 10T+ 1 Oif. 



Amphicycbis 14(T + T') + 10#. 



Actinocucumis 16 to 18(T + T') + 2if. 



OrcuJa 10 to 15(T + T') + 5if. 



Phyllojihorus 12 to 16(T + T') + 5 to 6^ '. 



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 lOT, ST + 2t, and lOT+lOif ; 

 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. 



An inspection of this table shows that the forms are now seen to 

 he too closely and intimately allied to allow of the sharp differentia- 

 tion 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 Dendrochirotee ; and, after all, it is better for us 

 to recognize the tangled web and woof of the animal kingdom tlian, 

 in these days, to be content with definitions overloaded with excep- 

 tions, or distinguishing marks that tell us nothing of the past, and 

 give us but uncertain aid in the present. The day of linear classi- 

 fications is gone. 



3. An Account of the Land and Freshwater Mollusca col- 

 lected during the Voyage of the ' Challenger ' from 

 December 1873 to May 1876. By Edgar A. Smith. 



[Eeceived April 4, 1884.] 



(Plates XXII. & XXIII.) 



The object of the voyage of the 'Challenger' havmg been " to in- 

 vestigate scientifically the physical conditions and natural history of 

 the deep sea all over the worhl," 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 col- 

 lecting, but only such species appear to have been picked up as pre- 

 sented themselves to members of the scientific staff when on shore at 

 the various localities. The whole collection comprises only 1.52 

 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 



^ Echinocucumis would apparently have the formula of 8;'+2T, and is possibly 

 a slightly degi-aded form ; I have omitted it from the phylum. 



