conchology vs malacology

conchology and malacology both are nouns.

Word	Noun	Adjective	Verb	Adverb
conchology	Yes	No	No	No
malacology	Yes	No	No	No

As nouns, malacology is a hypernym of conchology; that is, malacology is a word with a broader meaning than conchology:

conchology: the collection and study of mollusc shells
malacology: the branch of zoology that studies the structure and behavior of mollusks

Other hypernyms of conchology include aggregation, assembling, collecting, collection.

conchology (noun)	malacology (noun)
the collection and study of mollusc shells	the branch of zoology that studies the structure and behavior of mollusks