114 
Fig. 3. Hydatina physis (Linnaeus), dorsal and ventral 
aspects (ca. X 1.3). 
Animal large and when active about three 
times as long as its shell. Head disc with four 
lobes of about equal size bluntly pointed at 
their tips. Two large, ear-like lobes extending 
posteriorly from head disc, partly covering 
anterior part of shell. Foot very broad and 
continuous with dorsally directed parapodial 
lobes; truncate at both ends, widest posteri- 
orly. Parapodial lobes much folded along 
margins, which are partly flexed over shell. 
Foot, both dorsally and ventrally, bluish pur- 
ple, merging into a vivid brown toward mar- 
gins. Head disc, anterior lobes, and mantle 
vivid brown, edged like anterior and posterior 
margins of foot with bluish or greenish white. 
Eyes conspicuously placed posterior to head 
disc. Gill pale bluish purple, turned inward 
at tip, and about 5 mm. in length, with 18 or 
20 plumules. Length of animal about 4 cm.; 
length of shell 16 mm. 
The specimen here described and figured 
was obtained during the latter part of June, 
1922, at Kawailoa, Oahu, where it was found 
among a number of Hydatina amplustre. Other 
specimens have been found off the Hawaii 
Marine Laboratory at Waikiki. 
The characters of the shell correspond well 
with those of the typical form figured and 
described by Tryon and Pilsbry (1893: 387, 
pi. 45). The description is as follows: 
PACIFIC SCIENCE, Vol. IX, April, 1955 
Shell large, globose or oval, thin; under a thin buff 
cuticle the shell is white, with many close wavy brown 
spiral lines. Surface very slightly and coarsely waved 
longitudinally, otherwise smooth. Vertex flat, the spire 
about level; whorls about 3V2, the first a minute globose, 
uptilted and half immersed nucleus, the rest separated 
by deep sutures. Body-whorl globose above, somewhat 
attenuated below, where there is a convex spiral rib 
surrounding the umbilical tract; aperture about as long 
as the shell, large, ovate, narrower and curved above, 
dilated below. Lip simple and thin, very little retracted 
toward its upper insertion, rounded at base, bluntly 
angled at foot of the columella. Columella gently con- 
cave or nearly straight, with reflexed edge, leaving an 
umbilical chink or rarely none. 
Spawn and the veliger stage of the larva 
are described and figured in Ostergaard 
(1950). 
Tethys elongata (Pease) 
Fig. 4 
Siphonata elongata Pease, Zook Soc. London, 
Proc. 1860: 24. 
Tethys elongata Pease. Tryon and Pilsbry, Man. 
Conch. 16: 93, pi. 59, figs. 35-38, 1895-96. 
Because of the rather strikingly different 
coloration of some of my specimens of this 
animal, they might appear to be different from 
the specimens of T. elongata (Pease), which is 
common on seaweeds along the leeward shores 
of Oahu; but after a study of them and a 
comparison with typical forms, I concluded 
that they constituted a color variation, merely, 
as no different characters could be discerned 
either in their external anatomy or shell. 
I enter herewith a description of this color 
form: 
Body elongate fusiform, slender, terminat- 
ing posteriorly in an obtuse point. Rhino- 
phores erect with acutely pointed extremities, 
and widely slit throughout the distal half of 
their length. Anterior, or labial, tentacles in- 
volute, broad and flaring in their proximal 
half. Foot rounded anteriorly and obtusely 
pointed posteriorly. Parapodial lobes high, 
ample, and folded, occupying the middle 
third of the body. To the left of the mantle, j 
from which the wide, flaring siphon extends, 
can be seen a portion of the shell. Genital 
