Ramdin, a veteran of 74 Tests, said he had been dropped because the selectors did not think his batting average was good enough. He has scored 2,898 Test runs at an average of 25.87.
"New chairman says my avg isn't good," Ramdin tweeted, referring to new West Indies chairman of selectors Courtney Browne, who has replaced Clive Lloyd.
Ramdin's comments earned a sanction from the West Indies Cricket Board (WICB) for a breach of the terms of his retainer contract, the board said.
Dowrich, 24, has played two Tests, against Australia in the Caribbean last summer, though he was used then as a specialist batsman, with Ramdin keeping wicket.
The 12-man squad again does not include several of the most dynamic West Indies players, such as Chris Gayle, Dwayne Bravo, Darren Sammy and Kieron Pollard, whose focus is on Twenty20.
Fast bowler Jerome Taylor is also missing after becoming the latest in a long list of players to quit the Test format.
West Indies' fortunes have diverged in recent years, with the Twenty20 team winning the world championship in 2012 and 2016, while Test performances have deteriorated sharply.
Fast bowler Jason Holder captains the team, which also includes the two batting heroes from the recent World Twenty20 triumph, Marlon Samuels and Carlos Brathwaite.
Squad: Jason Holder (captain), Kraigg Brathwaite (vice captain), Devendra Bishoo, Jermaine Blackwood, Carlos Brathwaite, Darren Bravo, Rajendra Chandrika, Roston Chase, Shane Dowrich, Shannon Gabriel, Leon Johnson, Marlon Samuels
Image: Denesh Ramdin
Photograph: Stu Forster/Getty Images
I have to accept that I didn't do well in shorter formats: Ishant
Kohli has created a positive team environment, says Mishra
When Ramdin took on Viv Richards...
When biscuits followed Gavaskar on Caribbean tour!
Shami pockets a cool 2.2 crore for putting Team India ahead of IPL