Run in GEMC

split -d -l 75000 -a 2 LUND_Spread.LUND LUND_Spread_

prename 's/(LUND_Spread_\d{2})/$1.LUND/' LUND_Spread_*

Placing each of these files into its own directory, within a directory named LUND_Spread

find . -name "*.LUND" -exec sh -c 'mkdir "${1%.*}" ; mv "$1" "${1%.*}" ' _ {} \;