gastracanthid (gastrakan′thid)

A spider of the family Gastracanthida. Gastracanthidæ (gas-tra-kan'thi-dē), n. pl. [NL., In gastræa (gas-trē'ä), n.; pl. gastræa (-ē). [NL., blastoporic communication with the exterior. In its simplest expre ion, a gastræa or gastrula represents a hollow sphere, or rather an hour-gla figure, with one half of it pushed into the other half, so that it makes a two-layered cup with a contracted opening. See emboly. The gastrula at the present day presents a correct picture of the primitive gastrœa , which must have developed from the Protozoa in the Lauren tian period. Haeckel , Evol. of Man (trans.), I. 249.