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140 Ainencan Seashells
3. Umbilicus closed by the callus, which passes smoothly into the base. .
(subgenus Idioraphe)
A. Periphery strongly carinate; 2 mm.; Destin, Florida. 20 fms.
goniogyrus Pils. and McG.
AA. Periphery rounded or indistinctly rounded.
B. Surface spirally striate:
C. Umbilical callus extremely convex and thick; 2 mm. Palm
Beach to Cape Florida pilsbryi McGinty
CC. Umbilical callus strong, slightly convex:
D. Strongly spirally striate throughout; 2.3 mm.; Key
Largo clavium Pils. and McG.
DD. Weakly striate above only; 1.5 mm.; southeast Florida
nesaemn Pils. and McG.
BB. No Spiral striations.
C. Diameter 1.8 to 2.2 mm.:
D. Rather globose, h/d ratio 75; shore to 50 fms.; southeast
Florida parvicallum Pils. and McG.
DD. Depressed, h/d ratio about 50:
E. Callus large. Lake Worth
obtectum Pils. and McG.
EE. Callus small. Biscayne Bay, shore
biscaynejise Pils. and McG.
CC. Diameter 0.7 to i.o mm.; callus thick; Lower Keys, shore
lereiJiujn Pils. and McG.
Superfa??iily CERITHIACEA
Family TURRITELLIDAE
Genus Tachyrhynchiis Morch 1868
Tachyrbynchiis erosinn Couthouy Eroded Turret-shell
Plate 21I
Nova Scotia to Cape Cod, Massachusetts. Alaska to British Columbia.
% to I inch in length, elongate, M as wide; 8 to 10 rounded whorls. No
umbilicus. Aperture round; columella smooth, slightly arched. Whorls with
5 to 6 smooth, flat-topped, spiral cords between sutures. Color cream to
chalky-white, with a thin, polished, gray-brown periostracum. Operculum
round, multispiral, chitinous, dark-brown. Common from 10 to 75 fathoms.
T. reticulatum Mighels (Arctic Ocean to Maine; and Alaska) is similar.