[a. F. frustule, ad. late L. frustulum, dim. of FRUSTUM.] The siliceous two-valved shell of a diatom, with its contents.
1857. Berkeley, Cryptog. Bot., § 103. 130. The frustules, which are long and slender, slip over each other, yet so as always to adhere, so that the whole mass is in motion, though at the same time several groups of frustules are moving in contrary directions.
1867. J. Hogg, Microsc., II. i. 278. Each frustule is however a perfect unicellular plant.
1876. Page, Adv. Text-bk. Geol., iii. 67. Diatomaceæ, of vegetable origin, whose frustules are also of silex.
