218 
PACIFIC SCIENCE, Vol. XX, April 1966 
and prominent transverse sculpture of indented 
lines. The texture is smooth, but very dull com- 
pared with the high polish of mature shells. As 
more whorls are added the umbilicus gradually 
closes, and one side of the shell becomes flat- 
tened. The plane of the aperture utlimately co- 
incides with the peripheral flattening of the 
shell. These two features, the closing of the um- 
bilicus and peripheral flattening of the shell, 
are as much a hallmark of determinate growth 
as the terminal elaboration of the aperture, 
which is also present in this genus. Figures 6 
and 7 were drawn from specimens in trans- 
mitted light, revealing the internal structure of 
the mature shell. After all the whorls of the shell 
have been formed, the whole of the outer sur- 
face of the shell is covered with a thin, color- 
less, polished, and glassy layer of shell material, 
I 
I 
N 
so that not only the sculpturing of the early 
whorls, but also the sutures, are obliterated. 
Figure 8 shows a fragment of a mature shell 
with the hyaline secondary layer obliterating the 
suture. 
The animal of the Ulithi species was not ob- 
served, but several mature, preserved specimens 
of P. ( Kanapa ) brazieri Crosse, from unknown 
locality, were studied. These had the mantle 
margin thin, flush with the lip of the shell, and 
without papillae or other appendages. The 
cephalopedal mass was typical of a cyclophorid, 
with no appendages which might have been 
reflected over the shell. Exactly how this hyaline 
layer is formed must await study of the live 
animal. It seems to be a generic or family 
characteristic, developed independently in such 
groups as the Cypraeidae. 
FIGS. 4-8. Pupina complanata: 4 and 5, juveniles. 6 and 7, two views of the same shell as seen in trans- 
mitted light, to show internal structure. 8, a fragment of a mature shell, showing the relation of the hyaline 
layer to the shell’s structure. 
