![](/drem/stage20/labels2/S31L.gif)
![artifact separation(s), intermediate zone, marginal zone, osteogenic layer, roof plate of mesencephalon, subarachnoid space, surface ectoderm](/drem/stage20/Z0/S31N.jpg)
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Carnegie Embryo #462 | Location: 1-01-01
Keywords: artifact separation(s), intermediate zone, marginal zone, osteogenic layer, roof plate of mesencephalon, subarachnoid space, surface ectoderm
Source: The Virtual Human Embryo.