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ACTEOCINIDAE 281
3 to 4 mm. in length, fragile, translucent-white, spindle-shaped, with a
sharp, long, spike-like apex. Glossy and with 4 or 5 very fine, indistinct,
punctate, spiral lines at each end. Outer lip thin, following the curvature
of the body whorl to just below the middle where it continues in a straight
line. Umbilicus chink-like. Periostracum thin and pale-straw. Common from
5 to 100 fathoms. R. bushi Dall comes from deep water off North Carolina.
It is larger, with a long apical process and with a long, chink-like umbilicus.
The genus Volvulella Newton 1891 is Rhizoriis.
Rhizorus acutus Orbigny Spined Spindle-bubble
North Carolina to southeast Florida and the West Indies.
Plate 26I
2 to 3 mm. in length, spindle-shaped, rather oblong, fragile, except for
minute spiral lines at each end. Upper end of aperture ends in a very sharp,
rather prolonged spike. Umbilicus rarely, if ever, present. Commonly
dredged down to 150 fathoms. R. 7ni?iutus Bush is probably the young.
R. aspinosiis Dall from the same region has the process poorly developed,
and may be a form of this species.
Fantily SCAPHANDRIDAE
Genus Scaphander Montfort 18 10
Scaphander piinctostriatus Mighels Giant Canoe-bubble
Arctic Seas to Florida and the West Indies.
Plate 26-0
I to 1% inches in length, very lightweight, but moderately strong.
Ovate-oblong. Apex with a slightly sunken area. Aperture constricted
above, roundly open below. Columella simple, rounded. Shell smoothish,
except for numerous, spiral rows of microscopic, elongate punctations. Color
chalk-white, with a straw periostracum. Fairly common from 20 to 1000
fathoms.
Scaphander 720 bills \^errill (Noble Canoe-bubble) from off New Eng-
land is the same size or smaller, has a proportionately much larger aperture,
its outer lip is wing-like above, and the microscopic punctations are round.
It is uncommon. A figure of S. luatsoni Dall is on plate 26m.
Family ACTEOCINIDAE
Genus Acteocina Gray 1847
Acteoci'ua culitella Gould Western Barrel-bubble
Kodiak Island, Alaska, to Lower California.