462 
BULLETIN OE THE UNITED STATES FISH COMMISSION. 
Superfamily PTERIACEA 
Family PINNID4E. 
Genus PINNA (Linnaeus) Lamarck, 1799, 
Shell thin, attached by a byssus, elongate, triangular, not auriculate, with pointed terminal 
beaks; posterior part truncated, gaping; ligament linear, elongated, lodged in a furrow. The middle 
of the shell is longitudinally sulcate and the inner nacreous layer is deeply bilobed at this sulcation. 
Pinna carnea Gmelin. 
Pinna came aGmelin, Syst. Nat., p. 3365, 1792. 
Pinna flabellum Reeve, Conch. Icon., pi. x, fig. 18, 1858 
Mayaguez, Porto Rico (Gundlach). 
Genus ATBINA Gray, 1840. 
Shell attached, elongate, triangular, thin, with pointed terminal beaks, truncated or rounded 
posteriorly, generally more or less covered with scales; valves unsuleate or without a median carina, 
and the internal nacreous layer is entire. 
Atrina. rigida Dillwyn. 
Pinna rigidci (Solander mss.) Dillwyn, Cat., I, p. 327, 1817. 
Pinna subviridis Reeve, Conch. Icon., Pinna, pi. xvii, fig. 32, 1S58. 
Shell somewhat elongately triangular, thin or somewhat thickened, slightly inflated; hinge line 
straight or incurved; ventral margin rounded at the middle; posterior end truncate or sub truncate, 
gaping; all of the shell except the ventral region is covered with low radiating ribs, which may be 
smooth or covered with more or less elevated scales; the scales sometimes become elongated and 
almost tubular; ventral area smoother, without ribs, often having prickly scales; inner layer smoky 
brown, faintly iridescent. Color blackish, olive brown, or ashy. 
Length, 25; height, 13; diameter, 4 cm. Mayaguez Harbor, Porto Rico, two fragments and a 
young shell. 
Family MEL1NID4E. 
Genus MELINA Retzius, 1788. 
Shell attached, subequivalve, inequilateral, compressed, with a posterior wing, somewhat sub- 
rhomboid or subquadrate; ligament multiple, lodged in a series of vertical, parallel pits along the 
hinge line; muscular impression subcentral; right valve with a byssal sinus below the hinge. 
Melina alata Gmelin. 
Oslrea alata Gmelin, Syst. Nat., p. 3339, 1792; Chemnitz, Conch. Cab., vii, pi. 59, fig. 581. 
Perna ephippium Reeve, Conch. Icon., xi, pi. n, fig. 8, 1858. 
Shell subquadrate or sub trapezoidal, greatly compressed, moderately solid; right valve nearly 
flat; left valve slightly convex; posterior wing low; hinge line short, with from seven to fifteen pits 
in each valve; left valve much thickened in front below the hinge; the right with a small byssal sinus 
opposite the swelling; exterior either nearly smooth or somewhat scaly; inner pearly layer of the 
shell not reaching the shell border. Color brownish, purple, or blackish, often marked with lighter 
color and white on the earlier part of the shell, which, when young, is sometimes rayed. 
Length, 80; height, 80; diameter, 8 mm. 
Puerto Real; Mayaguez, Porto Rico; Ensenada Honda, Culebra. At the former locality great 
numbers of fine specimens were found attached to the roots of mangroves and to each other. 
Melina listeri Hanley. 
Perna listen Hanley, 111. Cat. Rec. Biv. Shells, p. 259, 1846; Lister, pi. 228, fig. 63. 
Shell irregular, subquadrate, greatly drawn out and developed at the base; hinge line with from 
three to seven pits in each valve; posterior wing small; sinus of the right valve wide and rounded; 
left valve fuller than the right. The base of the shell is developed into a long, irregular, tongue-like 
process of porcellanous matter; the nacreous part does not extend more than half way from the hinge 
to the base. Color ashy, brownish, or purple brown, irregularly rayed with lighter color. 
Length, 25; height, 60; diameter, 7 mm. 
Puerto Real; Mayaguez; Ponce; Guanica; Hucares; Arroyo, Porto Rico; Ensenada Honda, Culebra. 
