Protoconch
![An SEM image of the trochophore of Haliotis asinina 11 hours post fertilization, with calcified protoconch (pc) prior to torsion.](/Images/godic/202502/04/Haliotis_asinina_trochophore_protoconch4731.jpg")
![Protoconch of Haliotis asinina when the torsion is complete.](/Images/godic/202502/04/Haliotis_asinina_protoconch4731.jpg")
![Apical view of the whole shell.](/Images/godic/202502/04/Atlanta_lesueurii4732.png")
![Detail of apical view of the same shell showing clearly visible protoconch, that has 2¼ whorls](/Images/godic/202502/04/Atlanta_lesueurii_24732.png")
A protoconch (meaning first or earliest or original shell) is an embryonic or larval shell which occurs in some classes of molluscs, e.g., the initial chamber of an ammonite or the larval shell of a gastropod. The protoconch may sometimes consist of several whorls, but when this is the case, the whorls show no growth lines.