Eurynia dilatata shell description:

 “Shell elongated, generally solid, rarely inflated, sometimes subcompressed, decidedly inequilateral, usually a little higher in front and often arcuate, especially in an adult state; beaks not much elevated above the curved dorsal line, generally subcompressed, turned a little forward over a well-developed lunule, their sculpture a number of strong, often rude, subcorrugated, longitudinal bars, which are sometimes slightly doubly looped; posterior ridge well developed, subangular or rounded, curved and placed close to the dorsal line, rarely double and ending behind in a point of biangulation at or near the base of the shell; surface with uneven growth lines, sometimes concentrically sculptured; epidermis dull, greenish or yellowish-brown in young shells, darker when old, often faintly rayed in young specimens; left valve with two rather small, stumpy or subcompressed pseudocardinals; right valve with one, having occasionally a vestigial tooth in front of and behind it; laterals club-shaped, one in the right valve which is sometimes double and two in the left; beak cavities exceedingly shallow; dorsal scars immediately under the hinge; muscle scars deep; pallial line impressed, crenate; nacre deep purple, salmon, straw-colored or white, obliquely ribbed”(Simpson, 2014; Mather, 2007).