Notochordal membrane covering derived from notochordal epithelium. Its first indication is at NF stage 24, and it is a distinct membrane by NF stage 28[XAO:0001020].

uberon

notochordal sheath

UBERON:0013655

The notochordal sheath in amphioxus has a complex three-layered organization with the outer, middle and inner layer The outer and middle layer are composed of collagen fibers of different thickness and course, that correspond to collagen type I and collagen type III in vertebrates, respectively, and the inner layer is amorphous, resembles basal lamina, and is closely attached to the notochord by hemidesmosome junctions.