Following is not an external manifestation of enamel
Perikymata are transverse, wave like grooves, believed to be the external manifestations of Incremental Lines of Retzius. Enamel cuticle is a delicate membrane that covers the entire enamel of the crown of a newly erupted tooth but is probably soon removed after mastication. Enamel lamellae are thin leaf like structures that extend from the enamel surface towards DEJ.
Enamel tufts
Enamel lamella
Incremental lines of enamel
Enamel cuticle