Please answer a question about the following article about New Haven, Connecticut:

New Haven was home to one of the important early events in the burgeoning anti-slavery movement when, in 1839, the trial of mutineering Mende tribesmen being transported as slaves on the Spanish slaveship Amistad was held in New Haven's United States District Court. There is a statue of Joseph Cinqué, the informal leader of the slaves, beside City Hall. See "Museums" below for more information. Abraham Lincoln delivered a speech on slavery in New Haven in 1860, shortly before he secured the Republican nomination for President.

Exactly who were the slaves upon the Spanish slaveship?
Mende tribesmen