Obliquely trigonal, yellowish, with numerous fine commarginal riblets, inner shell layer with radially ribbed structure that shows on surface as fine radial striations; interior thinly nacreous, margin finely denticulate. North Carolina to Florida, West Indies, Gulf of Mexico, Caribbean Central America, South America (to Patagonia). Length 5 mm. Note: Also called Atlantic Nut Clam.

As Nucula crenulata var. obliterata
This species is very variable, and presents sometimes an almost smooth surface (as in the var. obliterata), and at others either a series of regular concentric waves or a more or less broken and irregular concentric sculpture, the whole being united by every variety of transitional features. The most nearly allied species is N. sulcata Bronn (not A. Adams), which is however less trigonal, grows much larger, and yet has a finer and more irregular sculpture, in which the concentric element is less dominant. The N. culebrensis of Smith agrees so well with young, regularly sculptured specimens of crenulata, that, taking the locality into consideration, I feel quite confident of their practical identity. The ordinary adult and many young crenulata are more coarsely and roughly sculptured, but this is not invariable, and the large number of specimens I have examined have given an excellent opportunity for comparison.
Station 44, 539 fms.; Yucatan Strait, 640 fms.; Station 2, 805 fms.; Station 226, 424 fms., near St. Vincent; Station 236, near Bequia, in 1591 fms.; and at Station 262, near Grenada, in 92 fms.; bottom temperatures ranging from 39°. 0 to 62°. 0 F.

Nucula crenulata A. Adams, 1856 Distribution: South Carolina to Florida, Texas; Brazil. Size: 6 mm (1/4 in). Crenulate Nut Clam DEEP WATER Description: Color tannish-brown; shape triangular-ovate; sculpture smooth with faint commarginal threads; ventral margin rounded and finely crenulate; hinge with narrow, interiorly inclined chondrophore; teeth on either side of umbo; anterior hinge wider and longer than posterior hinge; umbo appears to overlap edge of chondrophore. Habitat: Found infaunally in sandy mud. Found alive at depths of about 100 m (330 ft). Depth range 55 to 1280 m (180 to 4200 ft). Remarks: Along entire Texas coast. Similar to E. aegeensis, but teeth are different, posterior laterals broader, and dentition on ventral margin more pronounced. See Pulley (1952a, 1952c); Odé (1980b).