HYGINUS (surnamed GROMATICUS, from _gruma_, a surveyor's measuring-rod), Latin writer on land-surveying, flourished in the reign of Trajan (A.D. 98-117). Fragments of a work on legal boundaries attributed to him will be found in C. F. Lachmann, _Gromatici Veteres_, i. (1848). A treatise on Castrametation (_De Munitionibus Castrorum_), also attributed to him, is probably of later date, about the 3rd century A.D. (ed. W. Gemoll, 1879; A. von Domaszewski, 1887). HYGINUS, GAIUS JULIUS, Latin author, a native of Spain (or Alexandria), was a pupil of the famous Cornelius Alexander Polyhistor and a freedman of Augustus, by whom he was made superintendent of the Palatine library (Suetonius, _De Grammaticis_, 20). He is said to have fallen into great poverty in his old age, and to have been supported by the historian Clodius Licinus. He was a voluminous author, and his works included topographical and biographical treatises, commentaries on Helvius Cinna and the poems of Virgil, and disquisitions on agriculture and bee-keeping. All these are lost. Under the name of Hyginus two school treatises on mythology are extant: (1) _Fabularum Liber_, some 300 mythological legends and celestial genealogies, valuable for the use made by the author of the works of Greek tragedians now lost; (2) _De Astronomia_, usually called _Poetica Astronomica_, containing an elementary treatise on astronomy and the myths connected with the stars, chiefly based on the [Greek: Katasterismoi] of Eratosthenes. Both are abridgments and both are by the same hand; but the style and Latinity and the elementary mistakes (especially in the rendering of the Greek originals) are held to prove that they cannot have been the work of so distinguished a scholar as C. Julius Hyginus. It is suggested that these treatises are an abridgment (made in the latter half of the 2nd century) of the _Genealogiae_ of Hyginus by an unknown grammarian, who added a complete treatise on mythology. EDITIONS.--_Fabulae_, by M. Schmidt (1872); _De Astronomia_, by B. Bunte (1875); see also Bunte, _De C. Julii Hygini, Augusti Liberti, Vita et Scriptis_ (1846).