tec·tum 
(tĕktəm)
(tĕktəm)n. pl. tec·ta (-tə)
A rooflike structure of the body, especially the dorsal part of the midbrain.
[Latin tēctum, roof, from neuter past participle of tegere, to cover; see (s)teg- in the Appendix of Indo-European roots.]
tectal (-təl) adj.