Sea Shells 
of New Zealand 
Plate IIT 
No. 21 
Plate I 
No.2 
two scars for the adductor muscles on each valve. The 
Chamostrea is not a true oyster in any sense, and is unfit 
to eat. 
Auckland Harbour; Bay of Islands; Cook Strait; 
Chatham Islands. 
SPIRULA SPIRULA (spirula, diminutive of spira, a 
spire).—The Ram’s Horn shell. These exceedingly fragile 
white shells are occasionally thrown up on the beach in 
great numbers, but the animal itself is extremely rare; in 
fact, only one complete Spirula has ever been found, and 
that was picked up on the New Zealand coast by Mr. Percy 
Earl. They are found in all warm seas, and are sometimes 
driven ashore in the Gulf Stream on the coast of Cornwall 
and Devonshire, in the Old Country. The animal belongs 
to the Cephalopoda, the same order that the Octopus and 
the Nautilus are members of. The spiral coils are all on 
the same plane, and are not in contact with each other, as 
other spiral univalves; consequently there is no suture. 
The shell is divided into separate compartments, each 
septum being beautifully rounded and pearly, and fitted 
with a calcareous tube near to the ventral or inner side, 
and running along the entire length of the shell, traversing 
each compartment. This tube is popularly supposed to be 
for the purpose of filling the cells with water or air, by 
means of which the creature may be enabled to sink to 
the bottom or rise to the surface, an ingenious theory, but 
quite wrong. The tube which runs through the cells is 
closed and does not in any way communicate with them, 
so the air-and-water idea falls to the ground. As the grow- 
ing animal has to enlarge its shell from time to time, it 
shuts off the portion no longer required. Oliver Wendell 
Holmes has written a poem on the Pearly Nautilus, con- 
taining some beautiful thoughts inspired by the contempla- 
tion of that shell, which is constructed on the same lines 
as our little Spirula. They were his favourite lines, and 
are generally considered the finest he ever wrote. Too 
long for quotation here, the line, “Build thee more stately 
mansions, oh, my soul?” gives one some idea of the fine 
sentiment they express. 
Three distinct species of the Spirula have been found 
in different parts of the world, and it is curious to note 
that the shell in each case is precisely the same, the differ- 
ence being in the animal itself. It is about three-quarters 
of an inch across. 
Throughout New Zealand. Mount Maunganui. 
ARGONAUTA ARGO (Argonaut, a companion of 
Jason in the ship “Argo”).—The Paper Nautilus is one 
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