The August 8, 1967 memo from D.C. Fontana to Gene Roddenberry entitled "STAR FLEET -- 12 STARSHIPS" is reproduced on page 163 of the thirteenth printing. It lists the following vessels:
Enterprise
Exeter
Essex
Excalibur
Lexington
Yorktown
Endeavor
El Dorado
Excelsior
Saratoga
Constellation
The memo continues, "Alternates include the names of some famous fighting ships of the past, plus a couple of international variations we migh consider, Star Fleet being composed of a united service.
Hornet
Wasp
Farragut Mentioned as destroyed in "Obsession"
Hood
Bonhomme Richard
Monitor or Merimac, depending upon your loyalties
Tori (bird)
Lafayette
Ari (lion)
Krieger (warrior)
Please consider."
Bob Justman then replies with his list of preferences from Fontana's list: Enterprise, Essex, Excalibur, Lexington, Yorktown, Endeavor, Eagle, Constellation, Hornet, Wasp, Lafayette.
He mentions other nations that might be worthy of having candidates and even suggests a ship with a name that sounds of Vulcan origin.
Finally, on page 165, the list of names for starships is established as: Enterprise, Exeter, Excalibur, Lexington, Yorktown, Potemkin, Republic, Hood, Constitution, Kongo, Constellation, Faragut, Valiant, and Intrepid. "The latter four are listed as destroyed in various episodes."
Note that these ships aren't considered to be of the "Enterprise" class, but, according to the Fontana memo referenced above, part of the "Starship" class.
