Apple Computer Inc. trademarked a number of big cats this month, indicating that the company intends to continue its feline naming scheme for future Mac OS X upgrades.

According to the U.S. Patent and Trademark Office, Apple registered four new trademarks in early July: Cougar, Lynx, Leopard and Tiger. All four were filed under the "computer operating system software" category.

News of the trademarks was first posted last week to Mac site MacRumors.

At the Worldwide Developers Conference in June, Apple announced Mac OS X 10.3, also known by its cat-themed code name, Panther; Apple said it plans to ship the $129 Panther upgrade by the end of the year. eWEEK first reported the Panther sobriquet in August 2002.

For the most recent release of Mac OS X, Version 10.2, Apple broke with a tradition of secrecy and dubbed the upgrade "Jaguar" after its internal code name, promoting the name and featuring a furry, jaguar-spotted version of the Mac OS X logo on its retail packaging. (Apple hasn't announced such a logo for Panther; The company's Web site and press materials instead feature a sleek, metallic "X" designed to complement the upgrade's revised interface.)

The initial Mac OS X release bore the internal code name Cheetah, and Mac OS X 10.1, which shipped in September 2001, was referred to internally as Puma, although neither moniker was ever publicized. (Mac OS X 10.2 Server was code-named Tigger, sources said—another sobriquet that never saw the light of day.)

A representative for Cupertino, Calif.-based Apple could not be reached for comment.