Crested

Guinea Pig

The Crested is similar to the American, but has one rosette on the top of the head. According to ACBA standards, the Crest must be white, with no other white hair present on the animal. The ANCC (Australian National Cavy Council) recognizes two main groups of crested but another group is also present, the White crested. The American Crested and the English Crested. The American Crested must have a crest colour that is in contrast to the body colour. Usually this is white, but it could be any other colour. These are only recognized in the self colour. English Cresteds have a crest the same colour as the body. These are recognized in every colour and variety, with the exclusion of the "coated" breeds (longhairs and coarse coats).

http://en.wikipedia.org/wiki/List_of_guinea_pig_breeds