abumbrellar

abumbrellar, a. Zool.

(ˌæbʌmˈbrɛlə(r))

[mod. f. L. ab away from + umbrella, applied to the disk of Acalepha: cf. abactinal, aboral.]

In sea-blubbers: pertaining to that surface of the velum or marginal ridge, which is turned away from the ‘umbrella’ or disc, in opposition to the adumbrellar surface which faces the ‘umbrella.’