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Key to Species1. Abdominal segments II-IV with acute lateral margins 2Abdominal segments II-IV lacking lateral margins, abdomenround in cross section (Fig. 1) (Batrisinae, Batrisini) 52.(1) Last segment of maxillary palpi laterally angulate, previous twosegments with spine on outer face (Fig. 21) (Pselaphinae,Tmesiphorini10. Tmesiphorus costalisApical segment of maxillary palpi elongate, lacking lateralangulation or spines on previous segments (Figs. 20, 22) 33.(2) Last segment of maxillary palpi elongate, penultimate segmentangulate on mesal margin (Fig. 20) (Goniacerinae, Tychini9. Cylindrarctus bicornisLast segment of maxillary palpi enlarged, penultimate segmentmuch smaller (Figs. 22, 24) 44.(3) Antennal club of last three segments, penultimate antennomerelonger than wide, last segment of maxillary palpus withlongitudinal groove on inner margin (Fig. 22) (Pselaphinae, Tyrini) 11. Hamotus electraeAntennal club of last two segments, penultimate antennomeremuch wider than long, last segment of maxillary pal pus lackingany groove (Fig. 24) (Euplectinae, Euplectini)12. Trimioarcus musamator, n. sp.5.(1) Apex of metatibiae lacking elongate pencil of appressed setae(Fig. 18); all antennomeres more than twice as long as wide(Fig. 17)8. Texamaurops reddelliApex of metatibiae with elongate pencil of appressed setae (Fig. 11);with antennomere VIII distinctly less than twice as long aswide except texanus with VIII twice as long as wide (Figs. 3, 9)(Batrisodes) 66.(5) Eyes distinct, with 10 to 50 facets grouped together. 7Eyes apparently absent, possibly up to 10 disassociated palegranules in area where eyes should be 97.(6) Vertex of head and anterior portion of pronotum coarselypunctate; males with anterior margin of vertex angulate (Fig. 1);females with vertex coarsely punctate1. Batrisodes uncicornisBasal half of vertex and anterior portion of pronotum not coarselypunctate; males with anterior margin of vertex truncate tobroadly rounded (Figs. 3, 15); females with vertex at mostcoarsely punctate on antennal tubercles, area between vertexalfoveae smooth or sparsely granulate 88.(7) Males with anterior margin of vertex broadly rounded,penultimate antennomere with small fovea at base (Fig. 15);females with large eyes of more than 40 facetsMales with anterior margin of vertex broadly truncate,penultimate antennomere lacking basal fovea (Fig. 3); femaleswith small eyes of approximately 15 facets7. Batrisodes globosus2. Batrisodes clypeonotus243