ID Keys
*Images in development

Key to Thracia and Cochlodesma

Crack on umbonal region, lithodesma protrudes ventrally. Small juveniles may not exhibit a crack, but lithodesma will always protrude ventrally = Cochlodesma.
Go to #2
No crack on umbo, lithodesma confluent with dorsal margin = Thracia.
If no crack but lithodesma is not confluent with dorsal margin and protrudes ventrally see above.
Go to #3
Lithodesma is oval-shaped, shell outline oval/subtruncate
Cochlodesma praetenue
Lithodesma peg-like, shell outline subtrigonal
Cochlodesma tenerum
From Arctic: Iceland, Northern Norway, Sweden
Go to #4
From British continental shelf
Go to #5
Elongate, rostrate and truncate posterior
Thracia gracilis
Rounded triangular outline
Thracia myopsis
Rostrum on posterior, visible as a shaded area on dorsal side
Go to #7
No rostrum on posterior and posterior end is longer than anterior
Go to #6
Prominent moon-shaped lithodesma
Go to #8
Short, thin lithodesma, often lost
Go to #10
Pallial sinus is shallow
Thracia pubescens
Pallial sinus moderate - to beak
Go to #9
Posterior margin broadly curved
Thracia villosiuscula
Posterior margin truncated/straight
Thracia phaseolina
Short, squat shell
Thracia convexa
Shell ovate/elongate
Go to #11
Pallial sinus broad, points to anterior margin
Thracia villosiuscula
Pallial sinus narrow, points to dorsal margin
Thracia gracilis