204 IOWA STUDIES IN NATURAL HISTORY 
that the largest and best come to the market from Stewart Island 
at the extreme south of the Dominion. 
The sea-mussel (Mytilus) was also abundant on the shores of 
Rakino and doubtless at many other places on the New Zealand 
coast. I did not hear anything denoting its use as food by the 
colonials, although it is quite likely that the Maori used it. These 
shells were also used as foundations by many small barnacles and 
in some cases were almost entirely covered with the twisting 
shells of tube-dwelling worms. I could see no prominent points 
of difference between this mytilus and those of our own Pacific 
coast. A number of shells probably allied to Cardium were col- 
lected by Dr. Stoner at Waineki Island. 
Among the gastropods the most interesting find was a species 
of Xenophora. This species has the remarkable habit of cement- 
ing to the whorls of its shell a whole series of other shells usually 
of a single species. Those which came up in the trawl on the 
Cowan all utilized the same species, a small lamellibranch probably 
belonging to the family Veneride. These are arranged in close 
series around the distal whorls, quite evenly spaced and always 
with the concave or inner side up. Impressions throughout the 
entire spire of the Xenophora show that it commenced this style 
of ornamentation quite early in life, and it is evident that if all 
the shells remained in place there would be several whorls of them 
outlining the whorls of the host. Toward the apex of the spire, 
however, fragments of other shells are cemented on. Is it possible 
that Xenophora improved its method with age and experience and 
finally adopted a uniform ornamentation, by using the same bi- 
valves throughout, attaching all of them with the same surface 
upward? Or did it use the same shell throughout because it lived 
on a bottom where that shell is most abundant and perhaps the 
only available material ? 
In the volume of the Cambridge Natural History on Mollusca, 
p. 64, Rev. A. H. Cooke says: ‘‘The singular genus Xenophora 
protects itself from observation by glueing stones, shells and vari- 
ous debris to the upper side of its whorls. Sometimes the selection 
is made with remarkable care; the Challenger, for instance, ob- 
tained a specimen which had decorated its body whorl exclusively 
with long pointed shells.”’ 
It seems to me that this device is hardly protective as it renders 
the Xenophora more conspicuous than it naturally is. Neither 
can I conceive of it as decorative in any purposeful sense. The 
