Sussex leg-spinner Will Beer signs a new, undisclosed-length contract to remain at Hove in 2019.
The County Championship will see three teams promoted and one relegated next year to create a 10-team top tier from 2020.
Lancashire leg-spinner Matt Parkinson will miss England Lions' tour of the UAE with a stress fracture in his back.
Jason Gillespie says more batting consistency would have strengthened Sussex's Championship promotion chances.
Audio & Video
Laurie Evans' unbeaten 62 leads Sussex to a "very comfortable" five-wicket victory over Durham in the T20 Blast quarter-finals.
Analysis and opinion from the BBC's cricket correspondent.
How to follow cricket on the BBC
BBC Sport brings you live radio commentary from England's Test series against India.
Cricket alerts, newsletters and social media
Get latest scores and headlines sent straight to your phone, sign-up to our newsletter and learn where to find us on online.
How to get into cricket
How to get into cricket - physical exertion with a chess-like element in matches which range from half an hour to five days.