MOLLUSCA OF PORTO RICO. 
477 
Family SEMEUD4L 
Genus SEMELE Schumacher, 1817. 
Shell suborbicular or elliptical, slightly inequivalve; beaks small, curved forward; two cardinals 
in each valve; two distinct laterals in the right valve; resilium oblique, internal; ligament short; 
muscle scars large; sinus deep. 
Semele proficua Pulteney. 
Tellina proficua Pulteney, in H utchin's Dorset, p. 29, pi. v, fig. 4, 1799. 
Am.phidesma reticulata Reeve, Conch. Icon., vm, pi. v, fig. 29, 1853. 
Shell nearly equilateral, a little longer in front, suborbicular, a little longer than high, subsolid 
and subinflated; ligament small, placed in a sort of escutcheon; there is a decided lunule in front of 
the beaks; the posterior part, of shell is slightly flexed; surface sculptured with rather strong, 
concentric growth lines; these are sometimes elevated into ridges and have fine radial strife which 
give it a somewhat wrinkled appearance; left valve with two direct compressed cardinals, the anterior 
the larger, and two laterals; resilium pit deep; right valve with two cardinals, the hinder the larger, 
and two strong laterals. Color whitish, straw, or purplish, sometimes variegated. 
Length, 30; height, 27; diameter, 14 mm. 
San Juan, Porto Rico, one young specimen. 
Semele purpurascens Gmelin. 
Venus purpurascens Gmelin, Syst. Nat., p. 3288, 1792. 
Tellina obliqua Wood, Gen. Conch., pl.xi.i, figs. 1, 2, 1815. 
San Juan, Porto Rico (Gundlach). 
Semele bellastriata Conrad. 
Amphidesma beUastriata Conrad, .Tourn. Acad. Nat. Sci. Phila., vii, p. 239, pi. xx, fig. 1, 1837. 
Amphidesma cancellata d’Orbigny, Moll. Cubana, ii, p. 241, pi. xxv, figs. 42-44, 1845. 
Shell compressed, elliptical, the anterior side much the longer; surface covered with distinct, 
radiating ribs which are crossed by rather strong, concentric ridges that often form small tubercles 
where they meet the ribs; left valve with a strong bifid cardinal, with a faint lamellar one in front of 
it and two faint laterals; right valve with two cardinals, the posterior larger and slightly bifid, and two 
elongated, elevated laterals; pallial sinus deep and rounded. Color ashy purple, often rayed violet within. 
Length, 25; height, 20; diameter, 9 mm. 
Mayaguez, Porto Rico, one young, worn valve. 
Section SEMELINA Dali, 1900. 
Semele nuculoides Conrad. 
Amphidesma nuculoides Conrad, Am. Journ. Sci., XLi, p. 347, 1841; Pos. Medial Tert., p. 73, pi. 41, fig. 6, 1845. 
Shell small, solid, ovate, subcompressed, the beaks near to the anterior end; surface covered with 
fine, sharp, concentric ridges and a delicate, straw-colored epidermis; left valve with two divergent 
cardinals, the posterior slightly bifid, and a faint anterior lateral; right valve with two cardinals, the 
posterior bifid, and two strong laterals; pallial sinus large and rounded. 
Length, 4.5; height, 3; diameter, 1.5 mm. 
San Juan Harbor; Mayaguez, Porto Rico. 
Genus ABRA (Leach) Lamarck, 1818. 
Shell - rather compressed, oval, subtriangular or subquadrate, whitish, shining, smooth; posterior 
side shortest; resilium lodged in a cardinal pit; right valve with two cardinals and generally two 
lamellar laterals; left with one cardinal and sometimes a rudiment of a posterior lateral. 
Abra aequalis Say. 
Amphidesma, sequalis Say, Journ. Acad. Nat. Sci. Phila., ii, p. 307, 1822: Am. Conch., in, pi. xxvm, 1831. 
Shell somewhat quadrate, subinflated, rather thin; beaks nearer the posterior end which is 
subtruncated above; surface with delicate growth lines; smooth, dirty yellowish white, scarcely 
shining; left valve with one strong cardinal, a vestige of a second in front, and no laterals; right 
valve with one cardinal and a feeble one behind it, without laterals; pallial sinus deep. 
Length, 10; height, 8; diameter, 4 mm. 
Mayaguez Harbor, Porto Rico. 
