THE ''SAILING'' OF THE NAUTILUS. 95 



at the bottom, principally on crabs ; and, as Dr. S. P. 

 Woodward says, in his 'Manual of the Mollusca,' "perhaps 

 often lies in wait for them, like some gigantic sea-anemone, 

 with outspread tentacles." The shape of its shell is not 

 well adapted for swimming, but it can ascend to the surface, 

 if it so please, in the same manner as can all the cuttles — 

 namely, by the outflow of water from its locomotor tube. 

 The statement that it visits the surface of the sea of its own 

 accord is at present, however, unconfirmed by observation. 

 But, if the Pearly Nautilus is the inferior and poor rela- 

 tion of the argonaut, it lives in a handsome house, and 

 comes of an ancient lineage. The Ammonites, whose 

 beautiful whorled and chambered shells, and the casts of 

 them, are so abundant in every stratum, especially in the 

 lias, the chalk, and the oolite, had four gills also. These 

 Ammonites and the Nautili were amongst the earliest 

 occupants of the ancient deep ; and, with the Hamites, 

 Turrilites, and others, lived upon our earth during a great 

 portion of the incalculable period which has elapsed since 

 it became fitted for animal existence, and in their time 

 witnessed the rise and fall of many an animal dynasty. 

 But they are gone now ; and only the fossil relics of more 

 than two thousand species (of which 188 were Nautili) 

 remain to tell how important a race they were amongst the 

 inhabitants of the old world seas. They and their con- 

 geners of the chambered shells, however, left one represen- 

 tative which has lived on through all the changes that have 

 taken place on the surface of this globe since they became 

 extinct — namely, Nautilus povipiliits, the Nautilus of the 

 pearly shell — the last of the Tetrabranchs. 



I need offer no apology for endeavouring to explain the 

 difference between the Nautilus of the chambered shell and 

 the argonaut with the membranous arms which it was 



