Representatives of the family Tetragonicipitidae encountered in samples from marine and lagoonal localities on the Yucatecan continental shelf are described. Ph. yucatanensis n. sp. is added to the furciger species-group of the genus Phyllopodopsyllus. Resulting from the discovery of four new species which, at first sight, show close resemblance with the species known in the genus Diagoniceps Willey, a review of the genus is presented. Initially, the type-species of the genus Diagoniceps, D. laevis Willey, is redescribed in detail based on material from the Bahamas and specimens reported previously from Bermuda, type-region. Three out of the six previously described Diagoniceps species, i.e. D. bocki Lang, D.menaiensis Geddes, and Diagoniceps spec. Bodin are re-examined and redescribed. After comparison and discussion of the taxonomically important characteristics the following conclusions are presented: (1) Diagoniceps laevis Willey and D. mexicana n. sp., are retained in the genus; (2) D. bocki Lang, D. kunzi Marinov, and Diagoniceps spec., the latter considered here as a distinct species, named A. bodini n. sp., are assigned to the genus Aigondiceps n. gen., with D. bocki designated as type-species; (3) D. menaiensis Geddes and D. trifidus Yeatman are assigned to the genus Nidiagoceps n. gen., with the former designated as type-species; (4) Diagoniceps monodi Chappuis & Kunz is considered as species inquirenda; (5) the specimens reported from Bermuda by Coull and identified as D. laevis, represent an unknown species, O. elegantissima n. sp. which with O. xamaneki n.sp. and O. clarkae n. sp. constitutes the genus Odaginiceps n. gen. (O. clarkae n. sp. is proposed as type-species). In addition, the genus Godianiceps n. gen. is erected for G. maya n. sp. found in the famous Nichupté Lagoon near Cancun. Finally, an updated key to the currently recognised genera of the family Tetragonicipitidae is compiled.