MOLLUSCA OF PORTO RICO. 
429 
Genas BIVONIA Gray, 1842. 
Bivonia decussata Lamarck. 
Serpula decussata Lamarck, An. sans Vert., v, p.363,1818. 
Vermetus conicus var. decussatus Tryon, Man., vm, p. 170, pi. xt.ix, fig. 24, 1886. 
Quebradillas ( Gundlach ) . 
Family TURKITELLID^. 
* 
Genus TURRITELLA Lamarck, 1799. 
Shell greatly elongated, many-whorled and evenly tapering, sculptured with spiral .stria 1 or ridges; 
aperture rounded or subquadrate, entire, lip thin, externally flexuous; operculum horny, multispiral; 
nucleus central. 
Section HAUSTATOR Montfort. 
Turritella varieg-ata Linnseus. 
Turbo variegatus Linnaeus, Syst. Nat., ed. x, p. 767, 1758. 
Turritella variegata Reeve, Conch. Icon., v, pi. v, fig. 19, 1849. 
Shell with nearly flat whorls, but having the suture well marked by a slight shoulder above and 
below it; the sculpture consisting of fine, revolving threads and some seven or eight low but rather 
sharp ridges; aperture varying from rounded to subquadrate. Color pale brownish, variegated with 
indistinct longitudinal strigations of chocolate or purplish brown. 
Length, 70; diameter, 18 mm. 
Catona; Fajardo; Cabo Rojo light, Porto Rico; worn shells. 
Section TORCULA Gray. 
Turritella exoleta Linmeus. 
Turbo exoletus Linnaeus, Syst. Nat., ed. x, p. 766, 1758. 
Turritella exoleta Reeve, Conch. Icon., v, pi. vi, fig. 22, 1849. 
Shell with sixteen or seventeen whorls, which are rudely ridged above and below and concave 
in the middle; this concave space is sometimes crossed by thin lamellae; lower rib of the body whorl 
double; aperture sinuate in the middle of the outer lip, subquadrate. Color yellowish white, obscurely 
flamed with orange brown. 
Length, 60; diameter, 15 mm. 
Mayaguez, Porto Rico, two young, worn specimens. 
Family LITORINIDtE. 
Genus LITORINA Ferussac, 1821. 
Shell imperforate, turbinate, colored; aperture rounded, not notched below, the outer lip not 
thickened ; columella flattened or excavated ; operculum horny, paucispiral ; nucleus more or less 
excentric. 
Section MELARAPHE Muhlfeld, 1828. 
Shell rather thin, conical, with pointed spire; surface with revolving sculpture, usually variegated. 
Litorina ziczac Gmelin. 
Troclius ziczac Gmelin, Syst. Nat., p. 3587, 1792. 
Littorind ziczac Reeve, Conch. Icon., x, pi. xi, fig. 57, 1857. 
Shell with scarcely rounded whorls and a well-defined peripheral keel near the base of the last 
whorl; the whole surface is covered with delicate, rather widely spaced grooves; aperture small, 
irregularly oval; the thin lip extends upward above the keel on the body whorl, forming a canal; base 
a little produced. Color whitish, with close, sharply defined, longitudinal, wavy or zigzag stripes of 
brownish; sometimes the shell is faintly banded; aperture dark, with a light band. 
Length, 15; diameter, 9 mm. 
Aguadilla; San Geronimo; San Juan, Porto Rico; Ensenada Honda, Culebra, 
