TEE FAIRY SAILOR AND EIS COUSINS. 117 



None, save the " paper nautilus," have had external shells. 

 The animals of the lower order are incased in shells which 

 are long, tapering tubes, divided at regular intervals by 

 transverse partitions. The paper nautilus and his allies 

 have all lived in a later age of the 

 world than that of which I have been 

 speaking. The "pearly nautilus" is the 

 only living representative of the lower 

 order — an order which swarmed in the 

 seas of the Paleozoic and Mesozoic 

 Times. The pearly nautilus is closely 

 coiled (Fig. 46) ; its shell is divided at 

 frequent intervals by smooth partitions 

 concave anteriorly, the animal occupy- 

 ing only the space in front of the last 

 one. A shelly tube runs through the 

 middle of all these chambers to the far- 

 ther extremity of the shell. Through 

 this a ligament passes from the body of 

 the animal, and anchors it securely in 

 the last chamber. This tube is called 

 the siphon. Such is the structure of 

 the pearly nautilus, which may be seen WtAighSSSabered 

 in myriads, on a calm day, floating on of MesozSc' Tim™ be- 

 the surface of the waters of the South itegm1iy? theAmmon " 

 Pacific. 



The reader will certainly thank me for introducing here 

 a beautiful poem on "the Chambered Nautilus," though the 

 author has committed the error of supposing it was this 

 species of nautilus to which the Aristotelian fable of the 

 fairy sailor applied. 



" This is the ship of pearl, which, poets feign. 

 Sails the unshadowed main — 

 The venturous bark that flings 



