sb. pl. [L., neut. pl. of testāce-us adj., consisting of testæ, i.e., tiles, shells, etc.; also, covered with a shell: see -ACEA.]
† 1. Testaceous substances, as limestone, chalk. Cf. TESTACYE. Obs. rare–1.
1743. Lond. & Country Brew., III. (ed. 2), 241. Chalk and other Testacea will answer the same, but not so well.
2. Zool. A name for various groups of invertebrate animals having shells (excluding Crustacea). spec. † a. (a) used by Linnæus to designate his third order of Vermes, comprising the shell-bearing mollusks; (b) by Cuvier applied to the shell-bearing mollusks of his class Acephala. (Obs.) b. In present use, (a) A suborder of pteropod mollusks including all having calcareous shells, otherwise called Thecosomata; (b) an order of Protozoa having shells, with apertures through which the pseudopodia are protrusible.
1828. Stark, Elem. Nat. Hist., II. 4. In the last edition of his Systema Naturæ, Linnæus,… in the third and fourth divisions of his third order, Testacea, places those possessed of shells.
1830. Lyell, Princ. Geol., I. 52. Soldani … explained that microscopic testacea and zoophytes inhabited the depths of the Mediterranean.
1860. Hartwig, Sea & Wond., i. 11. Pholades and Lithodomas are marine testacea, that have the power of burying themselves in stone.
1888. Rolleston & Jackson, Anim. Life, 905. The Amœbina may be classified as…: 1. Nuda s. Gymnamœbæ: devoid of a test…. 2. Testacea s. Lepamœbæ: a test either chitinoid … or composed of chitinoid or siliceous plates cemented together.
