Rounded trigonal, almost as high as long, slightly skewed anterodorsally, with strong posterior ridge, inflated, white with brown-black periostracum, with 27-31 squared radial ribs each divided by fine incised line, corn-marginal ridges most apparent between ribs, umbones opisthogyrate, no byssal gape; interior white, margin strongly denticulate, cardinal area wide. Virginia to Florida, West Indies, Gulf of Mexico, Caribbean Central America. Length 50 mm (to 60 mm).

Noetia ponderosa (Say, 1822) Distribution: Virginia to Florida, Texas. Size: 51 to 76 mm (2 to 3 in). Ponderous Ark Description: Color uniformly white, hirsute brown periostracum; shape in- flated, thick, trapezoidal, widely ovate; sculpture of flattened, grooved radial ribs with fine concentric threads between radials; hinge line straight; ligament area relatively broad with numerous various-sized teeth, anterior teeth angled; inner ventral margin serrate; posterior adductor muscle scar raised to form a rim. Habitat: Coastal bays and sandy bottoms offshore at depths from below tide line to 68 m (223 ft). Remarks: One of the most widespread bivalves on the entire Texas coast. See Odé (1978c); Rehder (1981).