494 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
of the concentric ridges; left valve with two cardinals, two anterior and two posterior laterals; right 
valve with two cardinals, one anterior and one posterior lateral; beak cavities moderately deep. 
Color white, yellowish, or salmon. 
Length, 12; height, 13; diameter, 8 mm. San Juan Harbor, Porto Rico. 
The deep sulci, usually three in number, seem to indicate resting stages. The typical Irisulcatus 
is a Miocene fossil. 
Subgenus Lucinisca Dali, 1901. 
Phacoides muricatus Spengler. 
Tellina muricata Spengler, Skrift. Nat. Selsk., 1798, p. 120. 
Lucina scabra Lamarck, An. sans Vert., vi, p. 542, 1819; Reeve, Conch. Icon., vi, pi. vrn, tig. 45, 1850. 
Shell suborbicular, compressed, rather solid, slightly truncated posteriorly, with numerous 
radiating rows of ridges alternately larger and smaller, the larger and sometimes the smaller rows 
beset with elevated, prickly scales; beaks pointed forward and having a few concentric lamellse; lunule 
small; left valve with two cardinals, two anterior and two posterior laterals; right valve with two 
cardinals, the anterior bifid, with one anterior and one posterior lateral; anterior muscle scar long; 
posterior scar oval; border crenated. Color white. 
Length, 13; height, 12; diameter, 4 mm. Mayaguez Harbor, Porto Rico. 
Subgenus Lucinoma Dali, 1901. 
Phacoides radians Conrad. 
Lucina radians Conrad, Am. Journ. Sci., xli, p. 347, 1841. 
Lucina radiata Conrad, Fos. Medial Tert., p. 70, pi. xl, fig. 3, 1845. 
Shell suborbicular, subinflated, rather solid, with moderately high beaks, which are turned 
forward over a deep lunule; surface everywhere covered with regular, concentric, fine, threadlike 
ribs, and these are cut by faint, radiating depressions; left valve with two radial, compressed cardinals 
and a feeble anterior lateral at the base of the lunule; right valve with one compressed cardinal, which 
is sometimes slightly bifid; beak cavities moderately deep, compressed; anterior muscle scar oblique, 
rather elongated; posterior scar oval; pallia! line deep; border of the shell crenate. Color white. 
Length, 18; height, 17.5; diameter, 10 mm. 
San Geronimo, Porto Rico, two worn valves. 
Genus DIVAKICELLA von Martens. 
Divaricella quadrisulcata d’Orbigny. 
Lucina quadrimlcata d’Orbigny, Voy. Am. Mer., p. 584, 1846: Moll. Cubana, II, p. 294, pi. XXVII, figs. 34-36, 1853. 
Shell nearly orbicular, the beaks projecting but slightly above the general outline, subsolid, 
somewhat inflated, with a very small, imperfectly developed lunule; surface sculptured throughout 
with rather sharp chevron-shaped ridges whose most elevated points are in a line running from the 
beaks to a little in front of the middle base; besides it is marked with faint, concentric growth lines 
and somewhat stronger rest lines; ligament nearly imbedded in a groove of the hinge; right valve 
with a divided cardinal and a feeble one in front of it; left valve with two cardinals; laterals wanting; 
borders of the shell finely, often feebly, crenulate. The shell is white throughout, covered, when 
perfectly fresh, with a thin, straw-colored epidermis. 
Length, 25; height, 24; diameter, 14 mm. 
ITucares, Porto Rico, one young worn valve. 
Very close to !>. dentata Wood, which has deeper rest marks and is strongly dentate at the rest 
periods and on the edges. 
Family CYRENELLIM. 
Genus CYREN0IDA Joannis, 1835. 
Cyrenoida americana Morelet. Plate 58, fig. 5. 
Oyrenoides americanus Morelet, Test. Nov., n, p. 26, 1851. 
Cyrendla americana Shuttleworth, Diagn. Neuer Moll., No. vu, p. 163, 1854. 
One specimen in the U. S. National Museum collection was contributed by Walton from Arecibo, 
Porto Rico, being part of the material from which the species was described. It was first discovered 
at the Isle of Pines, near Cuba. 
