myostracum

English edit

myostracum (plural myostraca)

(zoology) Part of shell wall secreted at attachment of adductor muscles.
- 1964, Shell Structure and Muscle Scars of Cap-shaped Archaeogastropods:
  At this place in the myostracum the smaller, second-order prisms […] range from two to 15 microns in diameter.
- 2014, Adolf Seilacher, Alan D. Gishlick, Morphodynamics, page 68:
  In contrast to the muscle scars, the growth tracks of which are marked by a radial stretch of myostracum, the growth track of the pallial line is the boundary surface between two shell layers.