MOLLUSCA OF PORTO RICO. 
493 
Genus MYRTIEA Turton, 1822. 
Myrtsea pristiphora, n. sp. Plate 55, tigs. 4, 6. 
Shell small, solid, white, moderately convex, with small, conspicuous beaks; surface of the beaks 
nearly smooth, the remainder of the disk sculptured with fine, concentric, close set, rather uniform 
lamellae, which, toward the hinge line at each end of the shell, become more elevated and sparser; 
at hinge line these lamellae in perfect specimens are produced into little triangular projections, which 
form a saw-like series along the hinge line; lunule lanceolate, very small and narrow; interior of disk 
punctate; lateral and cardinal teeth moderately developed, margins finely radially striate or smooth. 
Length, 7; height, 7.5; diameter, 4 mm. 
Mayaguez Harbor, Porto Rico, at station 6062, in 30 fathoms, sand; also in San Juan Harbor in 
45 fathoms, at station 123. 
Genus PHACOIDES Blainville, 1825. 
Shell suborbicular, white, solid, concentrically lamellated or sculptured, and often having radial 
or oblique sculpture; beaks compressed; margins smooth or erenulate; hinge teeth, 2.2; laterals, 1.1 
and 2.2, or obsolete; muscular impressions rugose, the anterior elongated within the pallial line; 
umbonal area with an oblique furrow. 
Phacoides pectinatus Gmelin. 
Tellina pectinata Gmelin, Syst. Nat.., vi, p. 3236, No. 41, 1792. 
Lueina jamaicensis Lamarck, An. sans Vert., v, p. 539, 1818; Reeve, Conch. Icon., vi, pi. n, figs. 7, a, b, 1850. 
Shell suborbicular, scarcely inflated, rather solid, sculptured throughout with concentric ridges, 
which are sometimes close and irregular and at other times widely spaced and lamellar; beaks rather 
low, turned forward over a small lunule; ligament partly immersed in the hinge plate; there is a wide 
radiating furrow beginning at the lunule and ending in front in a decided sinus at the edge of the 
shell, and there is a radiating posterior depression just behind the posterior ridge; left valve with two 
small oblique cardinals, which are sometimes faint or wanting, with two anterior laterals, the lower 
the larger, and two very small remote posterior laterals; right valve with one oblique, small cardinal, 
which may be feeble or wanting, with one anterior and one posterior lateral ; cavity of the shell often 
radially rugose and slightly pust.ulose; anterior muscle scars long, narrow, and rather smooth; 
posterior scars oval. Color dirty white or pale salmon, within and without. 
Length, 55; height, 50; diameter, 30 mm. 
San Juan market, San Antonio Bridge, San Juan, Quebradillas, Porto Rico (Gundlach) ; West 
Indies and Florida; abundant in shallow bays, on sandy muddy bottom. 
Subgenus Here Gabb, 1866. 
Phacoides pensylvanicus Linnams. 
Venus pensylvanica Linnseus, Syst. Nat., ed. x, p. 688, 1758. 
Lueina pennsylvanica Reeve, Conch. Icon., vi, pi. vi, fig. 29, 1850. 
Shell suborbicular, inflated, solid, with rather high, sharp beaks turned forward over a large 
lunule, with a distinct radial posterior furrow, which ends in a sinus above the base; epidermis raised 
into numerous concentric, elevated laminae, the outer edges of the laminae developed into wide, 
refiexed fimbriations; ligament mostly imbedded; left valve with two elevated cardinals and one 
anterior and two posterior laterals; right valve with a bifid cardinal, a high anterior, and double 
posterior lateral; anterior and posterior scars elongated; cavity of the shell rough, sometimes pitted, 
having a diagonal, impressed line running from near the base of the ligament toward the anterior 
base. Color white throughout, the epidermis becoming brownish in old shells. 
Length, 54; height, 53; diameter, 40 mm. Mayaguez, Porto Rico, a number of young valves. 
The outline from the beaks to the anterior point of the shell is nearly straight or slightly incurved 
as a result of the deeply impressed lunule. 
Section CAVILUCINA Fischer, 1887. 
Phacoides trisulcatus Conrad, var. blandus Dali. Plate 58, fig. 13. 
Lueina trisulcata Conrad, Am. Journ. Sci., n. s., I, p, 404, 1846. 
Shell obliquely subtriangular, higher than long, with the beaks placed behind the center, 
considerably elevated, and arched forward over a decidedly deep lunule; ligament short, nearly buried; 
there is a shallow radial furrow on the posterior slope; surface finely concentrically ridged, also with 
three or four deeper sulci generally having traces of radiating grooves which do not cut to the bottom 
