a. Zool. [mod. f. L. ad to, at + UMBRELLA, applied to the disc of Acalepha, + -AR. Cf. adactinal, adoral.] In sea-blubbers: Pertaining to the upper surface of the velum or marginal ridge, which is turned towards the ‘umbrella’ or disc, in opposition to the abumbrellar or lower surface.
1881. E. R. Lankester, in Jrnl. Microsc. Sc., Jan., 131. The ectoderm of the adumbrellar surface of the velum.
