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VERMETIDAE 143
heavily beaded, spiral cord. Operculum, corneous, thin, paucispiral, brown
and with lamellate growth lines. Moderately common in sand below low-
water line. Known for years as A. granulata Lamarck which, however, is a
later name.
Architectonica krebsi Morch Krebs' Sun-dial
North Carolina to southeast Florida and the West Indies.
Plates 4-0; 2iy
% inch in diameter, similar to A. nobilis, but glossy-smooth on top
except for two microscopic spiral threads above the suture, with a smooth
rounded base and with its deep umbilicus bordered by 2 beaded spiral rows,
the innermost having about 30 bar-like beads (in contrast to 12 in nobilis).
Operculum chitinous, brown and multispiral. Uncommon from 16 to 63
fathoms. Provisionally placed in this genus.
Architectonica peracuta Dall Keeled Sun-dial
Southeast Florida and the West Indies.
Plate 4n; figure 2 2g
% inch in diameter, similar to nobilis^ but smaller, with the spire much
flatter, whorls almost smooth, periphery very sharp, and without color spots.
Rare in 45 to 73 fathoms.
Family VERMETIDAE
Genus Petaloconchus H. C. Lea 1843
Petaloconchus nigricaits Dall Black Worm-shell
West Coast of Florida.
Plate 2ie
Lives in closely packed colonies of long, worm-like shells about 2 to 4
inches in length; each tube is about % inch in diameter. Shells rarely coiled,
except at the beginning. Moderately fragile, gray to rusty-brown in color,
and weakly sculptured spirally and longitudinally. Colonies of this species
frequently form large reefs or banks.
Petaloconchus irregularis Orbigny Irregular Worm-shell
South half of Florida and the West Indies.
Plate 2 id
Similar to nigricans, but greatly coiled, and with heavier, larger shells
which are strongly rugose. Occurs in compact masses attached to rocks and
other shells. Color dark brownish. P. erectus Dall is smoother, pure white
in color, and with the last part of the tube sticking straight up from the