premise: the <mask> of Theocritus
hypothesis: the best context for <mask> here is One of the two main arteries of the neck, by which blood is conveyed from the aorta to the head. [See Illust. of Aorta.]; but not A short poem; properly, a short pastoral poem; also, any poem, especially a narrative or descriptive poem, written in an eleveted and highly finished style.