Nutricola confusa
Similar to Nutricola tantilla. Nutricola confusa can be distinguished by its more prominent beaks, weaker teeth and weaker comarginal ribs. N. confusa also lacks the deep ray of color along the interior posterior dorsal margin found in N. tantilla.
Similar to Transennella conradina. Nutricola confusa is distinguishable by its rounder shape and less elongate posterior margin.
Similar to Transennella cubaniana. Nutricola confusa is distinguishable by its slightly pointed posterior margin; whereas, T. cubaniana has rounded margins. In addition, the ribs of T. cubaniana are thicker and more prominent than those of N. confusa. Their distribution is also different: species of the genus Nutricola, like N. confusa, are more likely found in cooler water than species of Transennella (Coan 2000).
The overall shape is subtrigonal ovate. The overall size is less than 10 mm. The posterior margin is slightly more pointed than the anterior margin. The anterior dorsal margin is nearly straight and the posterior dorsal margin is subconvex. The valves are equal in size and shape (equivalve), and there is no gape when they are closed. Sculpture consists of growth lines and very fine comarginal ribs. The lunule is lightly impressed, defined by a fine shallow groove and extends 2/3 of the anterior dorsal margin. The commissural margin is raised slightly at the center of the lunule, but it does not extend above the shell flank. The umbo is slightly anterior, and the beaks also point slightly to the anterior. The escutcheon is not well defined.
The external surface is white or dirty gray. There may be dark brown coloration along a few of the growth lines. The interior is white and may also have brown or purple coloration along a few of the growth lines.
The ligament is external, extends 1/4 the posterior dorsal margin and is supported by nymphal ridges. On the left valve, there are three cardinal teeth. The anterior (2a) and posterior (4b) teeth are not bifid, and the central tooth (2b) is lightly bifid. The anterior (2a) and central (2b) teeth meet dorsally, forming an inverted "V" shape. The posterior tooth (4b) is fused with the nymph. There is also one anterior lateral tooth (A2) on the left valve. On the right valve, there are three cardinal teeth. The anterior (3a) and central (1) teeth are not bifid, and the posterior tooth (3b) is lightly bifid. The central tooth (1) is trigonal in shape. There are also two anterior lateral teeth (A1, A3) on the right valve. There are fine, elongate oblique crenulations on the anterior, ventral and posterior margins. The anterior and posterior adductor muscle scars are similar in shape and size. The pallial sinus is round, and extends to the posterior end of the nymph in length.