MOLLUSCA OF PORTO RICO. 
483 
Superfamily VENERACEA. 
Family PETRICOEFDtE. 
Genus PETRICOLA Lamarck, 1801. 
Shell rude, nestling or boring; hinge without lateral teeth, with three left cardinals, the middle 
one larger and bifid; and two right cardinals, the posterior bifid; ligament external, pallial sinus 
present, shells earthy, usually white, the nepionic young sometimes bright colored. 
Petricola lapicida Gmelin. 
Venus lapicida Gmelin, Syst, Nat., VI, p. 3269, 1792; Wood, Index Test., pi. 8, fig, 72, 1825. 
Petricola costata Lamarck, Syst. An. sans Vert., p. 121, 1801. 
San Juan Harbor, Porto Rico, in dead coral. 
Family VENERlDiE. 
Subfamily VENERINAE. 
Genus VENUS Linnaeus, 1758. 
Shell thick, oval, generally inflated; valves ornamented with concentric ribs or lamella'.; lunule 
distinct; inner edge of the valves finely crenulated; hinge with three divergent cardinals in each 
valve, without laterals; pallial sinus deep, angular, ascending. 
Venus rugatina Heilprin. 
Venus rugatina Heilprin, Trans. Wagner Inst., i, p. 92, pi. xi, fig. 24, 1887. 
Shell large, irregularly short — elliptical or suborbicular, solid, inflated; umbonal region full; 
beaks turned forward and outward; lunule very deep and wide; there is a decided projection of the 
front part of the shell just below it; left valve with a sharp ridge near its upper posterior edge; in the 
right valve the corresponding ridge is low, and the shell overlaps the left valve at the lower part of 
this ridge. Surface covered with peculiar lamellar ridges in two series; there is a set of larger sloping 
ridges on which are developed from four to eight smaller ridges, all lamellate and having the lamella 
reflexed backwards; sometimes every seventh or eighth ridge is slightly stronger than the rest; left 
valve having the hinder cardinal lamellar, the middle bifid, and the anterior compressed, with a faint 
anterior tubercle; right valve with the posterior and middle cardinals slightly bifid, the anterior 
compressed; beak cavities deep and wide; pallial sinus small, angular; border crenulations fine. Pale 
brownish with a few faint, broad rays. 
Length, 90; height, 75; diameter, 60 mm. 
Mayaguez, Porto Rico, a number of young, worn valves. 
None of the recent specimens seen by the writers are more. than a fourth grown. It is found in 
the Pliocene beds of the Caloosahatchie, and the dimensions given above are from a specimen from 
that locality. 
? Venus rug-osa Gmelin. 
Veivus rugosaGmehn , Syst. Nat., p. 3276, 1792; Reeve, Conch. Icon., xi, pi. vn, fig. 23, 1863. 
San Juan, Porto Rico (Gundlach). 
This is perhaps the nearly allied V. rugatina instead of rugosa. 
Venus brasiliana Gmelin. 
Venus brasiliana Gmelin, Syst. Nat., p. 3289, 1792; Encycl. M6th., pi. 275, fig. 5. 
San Juan, Porto Rico (Gundlach). 
Venus cancellata Linnaeus. 
Venus cancellata LinnEeus, Syst. Nat., ed. xn, p. 1130, 1767; Reeve, Conch. Icon., xi, 1863, pi. xix, fig. 88. 
Shell somewhat triangular, solid, inflated, with a high posterior ridge and a long, wide, posterior 
groove; beaks almost flattened in the adult shells, pointed forward toward the well-marked lunule; 
surface sculptured with from twenty to twenty-five strong, concentric, lamellar ridges and with 
numerous well-defined radiating ribs, those in front often clustered; the space behind the posterior 
ridge is smooth. Color, ashy, sometimes irregularly rayed with brown; rarely the brown predomi- 
