SERIAL and Primary Key

CREATE TABLE "fav5"."batchnumber" (
"batchnumberid" SERIAL NOT NULL,
"processtype" SMALLINT NOT NULL,
"termloc" CHAR(3) NOT NULL,
"batchno" INTEGER NOT NULL
) WITHOUT OIDS;

With the above table definition, is batchnumberid by default also defined as the primary key or do I still need to define a separate Primary Key constraint?

Best Regards,

Michael Gould
All Coast Intermodal Services, Inc.
904-226-0978