Page:American Seashells (1954).djvu/190

3. Umbilicus closed by the callus, which passes smoothly into the base.

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(subgenus Idioraphe)

A. Periphery strongly carinate; 2 mm.; Destin, Florida. 20 fms.

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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

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pilsbryi McGinty

CC. Umbilical callus strong, slightly convex:

D. Strongly spirally striate throughout; 2.3 mm.; Key Largo

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clavium Pils. and McG.

DD. Weakly striate above only; 1.5 mm.; southeast Florida

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nesaeum 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

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parvicallum Pils. and McG.

DD. Depressed, h/d ratio about 50:

E. Callus large. Lake Worth

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obtectum Pils. and McG.

EE. Callus small. Biscayne Bay, shore

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biscaynense Pils. and McG.

CC. Diameter 0.7 to 1.0 mm.; callus thick; Lower Keys, shore

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leremum Pils. and McG.

 

Superfamily Cerithiacea
Family Turretellidae
Genus Tachyrhynchus Morch 1868

Nova Scotia to Cape Cod, Massachusetts. Alaska to British Columbia.

³⁄₄ to 1 inch in length, elongate, ¹⁄₄ 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,