Simplify the following text for a Grade 6 native English-speaking person.
Original: An enlarged and improved edition of his map of the volcanic region of Auvergne was published after his death , in 1823 , by his son Anselme GaÃ `` tan Desmarest ( 1784-1838 ) , who was distinguished as a zoologist , and author of memoirs on recent and fossil crustaceans .
Simplified: In 1823 his son Anselme GaÃ `` tan Desmarest published a new and better edition of his map .