Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† hippŏcampus or -os, i, m., = ἱππόκαμπος, a sea-horse: Syngnathus hippocampus, Linn.; Plin. 32, 11, 53, § 149; 32, 7, 23, § 67; 32, 9, 30, § 93; 36, 5, 4, § 26; Naev. and Lucil. ap. Non. 120, 17 and 19.