474 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
Sphenia antillensis, n. sp. Plate 55, fig. 14. 
Shell small, subquadrate, rather compressed, white, covered with a yellowish periostracum; 
surface dull, sculptured only by incremental lines and a low obscure thread running from the umbo 
backward and downward; shell thin, interior white, polished; hinge normal, general form as figured. 
Length, 4; height, 2.5; diameter, 1.5 mm. 
One perfect shell, Plava de Ponce, Porto Rico. 
There is nothing striking in the characters of this little shell, but it does not seem identifiable 
with any of the other species. The species from Cuba referred to this genus by d’Orbigny are referable 
to the genus Cuspidaria. 
Superfamily MACTRACEA. 
Family MACTRIDtE. 
Subfamily MACTRIN A£. 
Genus MACTRA (Linnaeus, 1758), Lamarck. 
Mactra fragilis Gmelin. 
Mactra fragilis Gmelin, Syst. Nat., p. 3261, 1792. 
Mactra fragilis Reeve, Conch. Icon., vm, pi. xi, fis. 47,1854. 
Mayaguez, Porto Rico (Gundlach). 
Mactra alata Spengler. 
Mactra alata Spengler, Skrivt. Nat. Selsk., v, pt. n, p. 99. 
Mactra alata Reeve, Conch. Icon., vm, 1854, pi. vm.fig. 29. 
Mayaguez, Porto Rico (Gundlach). 
Family MESODESMATIDtE. 
Subfamily ERVILIIN2E. 
Genus ERVILIA Turton, 1822. 
Shell small, concentrically striate, sometimes brightly colored; ligament obsolete; resilium 
small; laterals small; dorsal anterior lamina absent, the ventral more or less coalescing with the 
anterior arm of the right cardinal; left cardinal large, bifid; pallial sinus well marked. 
Ervilia concentrica Gould. Plate 58, fig. 12. 
Ervilia concentrica Gould, Otia Conch., p. 329; Proc. Boston Soc. Nat. Hist., vm, p. 280, 1862. 
Shell small, scarcely inflated, long-triangular, the posterior end narrower; beaks rather high but 
not full; surface finely, concentrically ridged, and having more delicate radial riblets which are most 
conspicuous on the anterior end; right valve with a single triangular tooth in front of the small, 
triangular resilium and a feeble one behind it; left valve with a double cardinal; pallial sinus faint, 
deep. Color whitish or pink. 
Length, 5; height, 3.5; diameter, 2 mm. 
San Juan; Mayaguez, Porto Rico, a number of worn valves. Off Georgia (Gould). 
Superfamily SOLENACEA. 
Family S0LENID4E. 
Genus PSAMMOSOLEN Risso, 1826. 
Shell transversely oblong, gaping at the extremities, obliquely sculptured, more or less invested 
with an epidermis; beaks subcentral; upper and lower shell margins nearly parallel; one or sometimes 
two cardinal teeth in each valve; ligament prominent; pallial impression large. 
