15 
Beside the Nautilus is her little cousin, the Spirula peroni, 
which sometimes, although not quite scientifically correct, is called 
an Ammonite. Our Nautilus is frequently found alive, but only 
one living specimen of this Ammonite has hitherto been caught, 
though several shells have been obtained from different parts of 
the world with portions of the fish attached. 
Neither towing nets nor dredges have been successful in 
catching the Ammonite, so it evidently does not live either on the 
surface or bottom of the sea, but probably between the two, in deep 
water. The shell is in a number of divisions, connected by a fine 
tube, and no doubt its use is to regulate the depth at which the 
animal wishes to stay. This the creature does by filling a number 
of the divisions with water or air, according as it wishes to sink 
deeper or float upwards. After a gale, on looking amongst the 
wrack cast up by the highest waves, large numbers of our Spirula 
will be found. Light and fragile the shells are, and they ride 
ashore without injury, and frequently are found covered with small 
barnacles, a proof that many weeks must have elapsed between 
the death of the owner and the casting ashore of its shell. In 
places in New Zealand, and elsewhere, large fossil deposits of 
Spirula peroni occur. It is worth remembering that, even though 
this shell is found as far away as England, the only living specimen 
was caught on the New Zealand coast. Our only other floating 
shells are three species of Janthina, or violet shells, two of which 
are shown on Plate VII., Figures 1 and 2. 
The first three shells on Plate II. belong to the Murex family. 
From this species the ancient Tyrians obtained a portion of their 
celebrated purple dye. The Janthina family (Plate VII.), how- 
ever, contributed the greater portion. The dye was extracted by 
bruising the smaller shells in mortars. 
MUREX ZELANDICUS (Plate II.).—Fig. 1 is known as the 
spider shell, from the spines, which look like spider’s legs. It is 
a white or greyish shell, about two inches in length. The long 
spines would interfere with the growth of this Murex if it had 
not the power of dissolving them as the outside of one whorl 
becomes the inside of the next. The removal is supposed to be 
assisted by chemical action, as the saliva of some shellfish is known 
