464 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
Ostrea cristata Born. 
Ostrea cristata Born, Mus. Vind., p. 112, pi. vii, fig. 3, 1780. 
Shell moderately solid, exceedingly irregular, elongated, rounded or oval; upper valve sometimes 
concave, at other times convex; lower valve convex; valves often furnished with elongated, tubular, or 
solid, clasping processes, by means of which the shell is attached to mangrove roots or other objects; 
edges of the valves strongly and sharply plicate-serrate, forming closely interlocking teeth; within, the 
border is often pustulose ridged, or striate; beaks very irregular, that of the lower valve the longer, its 
hinge area centrally grooved; muscular scars not deep. Color reddish, purplish, or brownish. 
Specimens attain a diameter of 90 mm. 
Gallardo Bank, Porto Rico. 
This species is even more irregular and variable in its growth than O. virginica. 
Ostrea frons Linnaeus. 
Mytilus frons Linnaeus, Syst. Nat., ed. x, p. 704, 1758. 
Ostrea frons Sowerby, Conch. Icon., xvm, pi. xix, fig. 41, 1871. 
San Juan, Porto Rico (Gundlach). The Ostrea 'parasitica Gmelin, credited to Porto Rico by 
Gundlach, is probably a form of 0. cristata Born. 
Family PECTIN I D4E. 
Genus PECTEN Muller, 1776. 
Shell suborbicular, inequivalve, not gaping nor attached, sculpture usually radial; auriculate; 
right valve convex, with a notch below the anterior ear, generally inflated at the beak; left valve con- 
cave, flat or slightly convex; hinge margins straight, united by a narrow ligament: resilium internal, 
in a central pit; adductor impression duplex. 
Subgenus Pecten s. s. 
Section EUVOLA Dali. 
Pecten laurentii Gmelin. 
Ostrea laurentii Gmelin, Syst. Nat., p. 3317, 1792. 
Pecten laurenti Reeve, Conch. Icon., viii, pi. xvi, fig. 58, 1853. 
Shell nearly orbicular, equilateral, rather thin, decidedly inequivalve, smooth and shining; left 
valve nearly flat in an anterior and posterior direction, but inflated in a direction from the beaks to 
the base, having a decided radial shoulder above on each side under the ears. It has very faint, low, 
wide, radiating ridges, and in addition minute radial threads, which are crossed by feeble concentric 
growth lines, ridged within with numerous radiating bars; right valve evenly convex, externally 
sculptured like left valve, with tine, radial ribs within arranged in pairs; ears nearly equal. The left 
valve is dark purplish red, with faint, radiating, lighter-colored rays; toward its upper part it is beauti- 
fully mottled with yellowish or pinkish white, and occasionally marked with oblique, light-colored 
strigations. There are also a few dark reddish-brown spots on the upper part of the shell. The right 
valve is whitish or buff, feebly rayed with brownish. 
Height, 90; length, 90 mm. 
A number of adult living specimens of this very tine and rare species were dredged in 7 fathoms 
in the harbor of Mayaguez. 
Pecten ziczac Linnseus. 
Ostrea ziczac Linnaeus, Syst. Nat., ed. x, p. 696, 1758. 
Pecten ziczac Reeve, Conch. Icon., viii, pi. vi, fig. 29, 1852. 
Shell rather solid, nearly orbicular, equilateral; left valve slightly concave, with a low but decided 
radiating shoulder on each side below the ears, with wide, low, distinct radiating ribs, crossed by 
faintly squamose growth lines, radiately ridged within around the border; right valve deeply convex, 
with widely spaced radiating grooves, the radiating ridges within inclined to be somewhat double; ear s 
nearly equal, slightly radially ribbed. Both valves with faint crura at the bases of the ears. Left 
valve painted with red-brown, buff, lilac and white, in broken, radiating patterns, brown bordered 
within; right valve reddish brown, becoming dusky at the border, marbled with white near the beaks. 
Length, 100; height, 90; diameter, 26 mm. 
Mayaguez Harbor, Porto Rico, one young specimen. 
