I'm doing a jigsaw of Speed's mid 17th century map of Sussex- from which I learn that Sussex is divided (or used to be divided) into administrative divisions known as "Rapes" which show up on the map between dotted lines. The Rapes may or may or not predate the Norman Conquest and consist of strips that run roughly north to south, following the course of rivers where possible. Counting off from right to left they are the Rapes of Hastings, Pevensey, Lewes, Bramber and Arundel.- the last one having been subdivided in the 13th century into the Rapes of Arundel and Chichester. Each of the ancient Rapes relates to a major Norman Castle. The origin of the name is disputed. If it's of Norman origin- from the French "raper" to seize"- it seems a little odd that no other English county adopted the system. Other possible derivations are from the Icelandic word hrepp, meaning a land division or the Anglo-Saxon "rap" meaning rope.
Local government using the Rapal system was never ended by fiat but simply faded away- with administrative duties passing to other bodies. The Rape of Hastings retained its own coroner as late as 1960.
There are six martlets on the county coat of arms- martlets being swallows or swifts (as featured in Macbeth)- each one standing for a rape.
The information that isn't derived from the map itself I got from here and here.