216 
PACIFIC SCIENCE, Vol XX, April 1966 
of it are from the Caroline Islands, he thought 
it was imported from Japan. 
Kororia palauensis Semper 
This species also occurs on Fais. Baker (1941) 
gave an account of the anatomy and distribu- 
tion. He thought this species was distributed by 
human agency. 
Family 8TREPTAXIBAE 
Gulella bicolor Hutton 
This species also occurs on Fais. Germain 
(1921) gave an extensive synonymy and other 
data on the occurrence of this snail in Mauritius. 
It is also found in India, Malaya, and several 
places in the Pacific islands. I collected it in 
Saipan in 1944 and in Puerto Rico in 1954. The 
University of Michigan Museum of Zoology 
has material from Brazil, French Guiana, Bar- 
bados, Panama, and elsewhere. It is undoubtedly 
a tourist snail, found in the same general area 
where Opeas occurs. The fact that it is less 
abundant and not so widely distributed as the 
latter may be due to its carnivorous habits. 
Order prosobranchia 
Family HYDROCENIDAE 
Hydrocena ( Georissa ) laevigata Quadras and 
Mollendorff 
Hydrocena (Georissa) laevigata Quadras and 
Mollendorff 1893, Nachr. d.d. Malak. Ges., p. 
42. Not figured. Type locality: Mariana Islands. 
This species was moderately abundant, and it 
also occurs on Fais. 
Shell (Fig. 1) thick, translucent, amber 
colored. It is dextral, conic-turbinate in shape, 
with the whorls evenly rounded, subcircular. 
Specimens of maximum size have an imper- 
forate umbilicus, and about three suture whorls. 
The initial whorl is smooth but not polished. 
It is usually separated abruptly from the 
later whorls by a transverse line, immediately 
beyond which there are numerous linear spiral 
grooves. On the apical part of the body whorl 
these become vague, and they usually do not 
continue on the later parts of this whorl, where 
they are replaced by faint incremental lines. The 
aperture is subcircular, its height being slightly 
shorter than the height of the spire. The outer 
lip is simple. In submature and mature shells 
there is a thick columella-parietal plate. 
The internal partition of the shell is partly 
resorbed ( Fig. 2 ) , leaving a narrow shelf which 
is apparently a remnant of the partition, and not 
a secondary structure, such as that of Pythia 
(Harry, 1951). The partition is complete about 
M whorl in from the aperture. The base of the 
cavity of the penultimate whorl extends down- 
ward to form a conical cavity behind the 
columello-parietal plate. 
The operculum (Fig. 3) is flattened, calcare- 
ous, semihyaline, smooth internally, and with an 
apophysis arising from the slightly elevated nu- 
clear area near the base. The apophysis is nar- 
row, elongate, directed obliquely outward in a 
gentle curve. It consists of two fused pieces, one 
not extending to the tip, but the line of fusion 
is vague. The outer surface of the operculum is 
covered by a thin, polished, horny layer, re- 
flected along the entire labial margin to form a 
narrow free membrane. The concentric lamina-, 
tion of the calcareous part, poorly defined and 
centering around a basal nucleus, is visible 
through the horny layer. 
Family PUPINIDAE 
Pupina complanata (Pease) 
Registoma complanatum Pease 1860, Proc. 
Zool. Soc. London, p. 440. Not figured. Type 
locality: "The Island of Ebon. Marshall's group/’ 
Dr. Cooke noted that the Ul.it.hi species was 
doubtfully present on Fais, and was nearer to 
P. complanata Pease than to P berenchleyi 
Smith 1891. Clench (1949) has recently mono- 
graphed this group, providing good descrip- 
tions and figures of both species. He recorded 
P. complanata from several localities in the 
Marshall Islands (type locality) and the Caro- 
line Islands. Mollendorff (1900) cited it as a 
traveling snail. 
The numerous shells from Ulithi present a 
partial growth series which reveals one of the 
most remarkable growth patterns to be found in 
land snails, and one which seems not to have 
been previously reported. The most juvenile 
shells (Figs. 4 and 5) have a definitely cyclo- 
phorid appearance, with an open umbilicus 
