MOLLUSCA OF PORTO RICO. 
425 
Family CERITHIIDiE. 
Genus CERITHIUM Bruguiere, 1789. 
Shell imperforate, turriculated, many-whorled, straight; aperture semioval, prolonged into a 
short, posterior canal above; canal at the base short, oblique, well marked; lip more or less thickened; 
columella concave; operculum horny, oval, paucispiral, nucleus submarginal. 
Cerithium algicola C. P>. Adams. 
Cerithium algicola C. B. Adams, Proc. Bost. Soc. Nat. Hist., n, p. 5, 1848. 
Cerithium algicola Tryon, Man., ix, p. 129, pi. xxii, figs. 81, 82, 1887. 
Whorls angular at the middle, sculptured with longitudinal ribs, which are developed into a 
more or less sharp knob where they cross the angle; surface covered with tine, revolving, raised 
threads; aperture rounded; columella concave. Color whitish, variegated with fulvous. 
Length, 20; diameter, 9 mm. 
Puerto Real, Porto Rico, two young shells; St. Thomas, two young specimens. 
Cerithium uncinatum Gmelin. 
Murex uncinatum Gmelin, Syst. Nat., p. 3542, 1792. 
Cerithium uncinatum Tryon, Man., ix, p. 127, pi. xxii, figs. CO, 61, 1887. 
Shell with revolving, thread-like sculpture, the middle of the whorls angular, with more or less 
perfectly developed longitudinal ribs, which generally develop into sharp knobs where they cross the 
angle of the whorls; the sculpture of the lower whorls sometimes consists of revolving rows of small 
nodules with intermediate threads; there is a varix on the body whorl opposite to the aperture, and 
scattered varices on the whorls; upper canal narrow; columella excavated ; basal canal short, recurved. 
Color white, variegated with brown or black, sometimes entirely white. 
Length, 22; diameter, 10 mm. 
Fajardo; Playa de Ponce; Puerto Real; Guanica; Arroyo; Boqueron Bay; Cabo Rojo light, 
Porto Rico; Caballo Blanco Reef, Vieques; Ensenada Honda, Culebra. 
A very abundant and variable species, which sometimes approaches the preceding one, but is 
generally more finely sculptured. 
Cerithium atratum Born. 
Cerithium atratum Born, Mus. Caes. Vind., p. 324, pi. XI, figs. 17, 18, 1780. 
Shell with a strong nodulous angle at the middle of the whorls, with a row of smaller nodules 
just below suture; the two rows of nodules sometimes united, forming short ribs; surface everywhere 
covered with strong, revolving, thread-like sculpture; upper canal small; basal canal short, reflexed. 
Color blackish, with broken, revolving white lines; aperture blue, becoming blackish farther in. 
Length, 25; diameter, 10 mm. 
Puerto Real; Mayaguez; Arroyo; Boqueron Bay; San Juan; Fajardo; Guanica; Ponce, Porto Rico; 
Ensenada Honda, Culebra. 
Cerithium litteratum Born. 
Cerithium litteratum Bom, Mus. Coes. Vind., p. 323, pi. xi, figs. 14, 15, 1780. 
Shell sculptured with numerous rather line nodulous revolving ridges; there is a shoulder just 
below the suture, on which the nodules are often quite strong; there is another nodulous shoulder 
just above the base of the body whorl; on the body whorl nearly opposite the lip there is a wide, low 
varix; outer lip thickened, ascending the penultimate whorl; aperture rather large; lower canal short. 
Color white, finely tessellated with black, the color pattern showing through within the aperture. 
Length, 20; diameter, 11 mm. 
San Juan; Guanica; Mayaguez; Fajardo, Porto Rico; Vieques; Culebra. 
Cerithium litteratum var. semiferrugineum Lamarck. 
Cerithium semiferrugineum Lamarck, An. sans Vert., vu, p. 74, 1822. 
Cerithium semiferrugineum Sowerby, Conch. Icon., xv, pi. Vi, fig. 38, 1865. 
In this variety the ground is white, sometimes more or less tessellated with brown, and variegated 
with yellowish brown. 
Vieques; Culebra; one shell from each locality. 
