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Family RISSOINIDAE
Genus RISSOINA D'Orbigny
1840. Rissoina D'Orbigny, Voyage dans !'Amerique Meridionale,
vol. 5, pt. 3 (Mollusques), p. 395.
1928. Rissoina D'Orbigny. Woodring, Carnegie Inst. Washington
Pub. 385, p. 362. An exhaustive treatment of the
Bowden Rissoina fauna with particular emphasis upon
the superspecific groups.
Type by monotopy: Rissoina inca D'Orbigny. Recent, off the
west coast of South America from Peru to the Island of Chiloe.
Outline rissoi'form, turriculate. Whorls nume;rous,
tapering gradually to the mammillar apex. Surface
axially or spirally ribbed, or cancellated, rarely smooth.
Aperture semielliptical. Outer lip retrocurrent, thickened,
slightly reflected, effuse, or faintly channelled
anteriorly. Columella nonplicate. Operculum thick,
horny, semilunar in outline, paucispiral, bearing a claviform
process upon the internal face.
The form of the operculum, the sinous outer lip, and
the depression of the anterior portion of the aperture
are distinguishing features of this genus. Like the
closely related Rissoa, which is usually more squat in
outline with a vertical instead of a retrocurrent outer
lip, Rissoina frequents the shallower waters where there
is abundant vegetation.
Subgenus SCHWARTZIELLA Nevill
1885. Schwm·tziella, Hand List Mollusca Indian Museum, pt.
2, pp. 73, 82.
Type by origmal designation: Turbo bryereus Montagu. Recent,
off the Florida Keys and in the West Indies.
The characteristic features of the subgenus are the
strong, protractive axials, the absence of a spiral sculpture
and the obscurely defined basal cord. Eurissolina
Woodring is similarly sculptured, but the basal cord is
much stronger, nicking the margin of the aperture, and
a second, much shorter cord is included between it and
the anterior extremity. The type of Ewrissolina is E.
ditomus Woodring, from the Bowden beds of Jamaica.
Rissoina (Schwartziella) harpa Gardner, n. sp.
Plate 29, figure 20
Shell minute, lustrous, white, elongate-conic in outline.
'Vhorls 7%, including the 21j 2 smooth, nuclear
turns. Whorls of the spire feebly convex but rendered
somewhat pseudoscalariform by the character of the
external sculpture; body gently rounded, feebly constricted
at the base. Axial sculpture only developed;
axials in the form of sharp, elevated, protractive ridges,
opposite in arrangement, extending from the anterior
suture almost, but not quite to the posterior, except on
the first sculptured volution; on the body whorl gracefully
recurved anteriorly and persistent to the margin
of the aperture; interradial areas broadly and evenly
concave, microscopically shagreened by the incrementals.
Whorls very closely appressed; the suture line
strongly undulated by the axials of the preceding whorl.
PART 2. SCAPHOPODA AND GASTROPODA 193
Basal cord distinct but not sharply defined. Aperture
holostomous, obliquely ovate, obtusely angulated posteriorly,
evenly rounded anteriorly. Outer lip flaring,
slightly patulous in front. Inner lip non plicate; aperture
lined uniformly throughout with a heavy glaze
which is reverted upon the pillar and along the anterior
margin.
Dimensions of holotype: Height 3.7 mm., maxinmm
diameter 1.6 mm.
Holotype: U.S.N.M. 325446.
Type locality: Walkers Bluff, Cape Fear River, Bladen
County, N. C. W accama.w formation.
Rissoina harpa is the possible antecedent of the later
Pliocene and Recent Rissoina chesnelii (Michaud) and
of the more slender, more closely ribbed subgenotype R.
bryerea (Montagu). It is most readily separated by
the character of the axial sculpture. The costae in the
'Vaccamaw form are more sharp and more prominent
than in either of the later species and instead of persisting
with undiminished vigor to the posterior suture
and impacting against the corresponding costae of the
preceding volution, they are abruptly constricted directly
in front of the suture line, thus lending to the
shell a pseudoscalar outline. The basal cord is possibly
better defined in the Waccamaw species than it
is in the Caloosahatchee and Recent forms, but this
character offers a rather wide range in individual
variation.
The species has been recognized at the type locality
only.
Family VITRINELLIDAE
Confusion is prevaient throughout the skeneid and
vitrinellid taxonomy. A knowledge of the animals is
essential for a correct classification, and without that
it seems hardly worth while to attempt an interpretation
of the tangled relationships of the genera included
under the Vitrinellidae and other families of small discoidal
forms. Two important series of papers are coming
out at the present time. 4 They are concerned exclusively
with the Recent species but are sure to throw
light on the relationships of their Tertiary ancestors.
Genus COCHLIOLEPIS Stimpson
1858. Oochliolepis Stimpson, Boston Soc. Nat. History Proc.,
vol. 6, p. 307.
Type by monotypy : Oochliolepis parasitica Stimpson. Recent,
in Charleston Harbor (type) and off the shores of the
Carolinas.
0 ochliolepis includes a small group of minute shells,
much compressed and paucispiral. The whorls increase
rapidly in diameter and are coiled like a ram's horn.
4 Pilsbry, H. A., and McGinty, Thomas L., Cyclostrematidae and Vitrinellidae
of Florida: Nautilus, vol. 59, No. 1, pp. 1-13, pis. 1, 2, July
1945; No.2, pp. 52-59, pl. 6, October 1945; No: 3, pp. 77-83, pl. 8, January
1946 ; vol. 60, No. 1, pp. 12-18, pl. 2, July 1946; to be continued.
Pilsbry, Henry A.; and Olsson, Axel A., Acad. Nat. Sci. Philadelphia
Proc., vol. 97, pp. 249-278, pls. 22-30, December 27, 1945.