Assertion: valve's thread | /r/HasProperty | secreted by gland
Facets:
value: on the foot
type: LOCATION
Source sentences:
text: A triangular form, ventral flattening, and secure attachment to firm substrates by byssal threads (byssus; proteinaceous threads secreted by a gland on the foot) have allowed certain bivalves to colonize hard surfaces on wave-swept shores.