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visible in dorsal view, with median elongate tuberclepointed at apex and rounded at base, top of tuberclenarrowly rounded, area immediately anterior andlateral to tubercle shallowly impressed and impunctate,minute vertexal foveae lateral to middle oftubercle, anterior margin of vertex broadly rounded,eyes with 13 facets, genal process lateral to maxillarybase bearing three setae, antennal club of apicaltwo antennomeres.Pronotum with biarcuate transverse antebasal sulcus,median antebasal fovea indistinct, distinct lateralantebasal foveae nude, large procoxal foveaemeeting internally; elytra with 2 basal foveae; withsmall lateral mesosternal foveae, otherwise sternalfoveae similar to those in figure by Grigarick andSchuster (1980) for Trimioarcus incisiurus Park;profemora with 7-8 sensory pits on ventral margin,mesotrochanters with broadly rounded angulation onventral margin, mesotibiae gradually expanded topast middle on mesal margin, abruptly constricted toapex, apex with angulate spine; only abdominal tergiteI with basal longitudinal carinae; sternite VIbroadly impressed at middle, penial plate with setaeon apical half.Females with vertex smoothly rounded laterallyand eyes easily visible, eyes with 13 facets, vertexalfoveae nude; legs lacking modifications; disc ofsternite VI broadly rounded.Holotype male: antenna 0.33 long, metafemora0.29 long, metatibia 0.30 long, aedeagus 0.22 long.Specimens examined.-7: TEXAS: TravisCounty: HOLOTYPE male, Twin Dig Pit, XII-l1­1990, J. Reddell, berlese rodent nests (FMNH).PARATYPES: 3 females, eutopotypical (DSC,TMMC); 1 male, 2 females, Moss Pit, III-5-1991,J. Reddell, M. Reyes, berlese litter from entrancepit bottom (DSC, TMMC).Etymology.- The name was suggested by thecollection from rodent nests.Comments.-This species was found in rodentnests in total darkness at the lowest point in TwinDig Pit, and in litter from the bottom of the entrancepit of Moss Pit (J. R. Reddell, pers. comm.).Trimioarcus Park (1952) was created to hold thenew species, incisiurus Park, from Monterrey,Mexico. A second species, pajarito, was recentlydescribed from southern Arizona (Chandler, 1985).Trimioarcus musamator is closest to incisiurus bythe broadly expanded head vertex with a medianprotuberance, and the eyes not visible in dorsal viewin the males. The two species differ in the form ofthe vertexal tubercle; and in musamator the smalleyes are of equal size with about 13 facets in bothsexes, and the middle legs modified in the male.This species looks very much like a member ofTrimiomelba LeConte, and would be readily placedin this genus except for the presence of lateralmesocoxal foveae and procoxal foveae.The reduction in eye size is probably a responseof this species to its exploitation of rodent nests ordeep leaf litter, rather than a response to the lack oflight in caves. No other members of the tribe Euplectiniare known to be cavemicolous, while anumber of species in a variety of genera in this tribehave reduced eyes and are found in deep leaf litteror tree holes.ACKNOWLEDGMENTSI would like to thank J. R. Reddell (Texas MemorialMuseum, Austin) for suggesting and assistingwith this study, and T.C. Barr, Jr. (College of BiologicalSciences, University of Kentucky, Lexington)for his contribution of many of the specimenscovered in this paper. I would like to also thankthose who arranged the loan of specimens: D.Azuma (Academy of Natural Sciences, Philadelphia),A.F. Newton, Jr. (Division of Insects,Field Museum of Natural History, Chicago), R.H.Turnbow (Fort Rucker, Alabama), and J.A. Wagner(Field Museum of Natural History, Chicago). C.E.Carlton, Department of Entomology, University ofArkansas, and J.F. Burger and R.M. Reeves, bothDepartment of Entomology, University of NewHampshire, reviewed the manuscript.LITERATURE CITEDBarr, T.C., Jr. 1974. The eyeless beetles of the genus ArianopsBrendel (Coleoptera, Pselaphidae). Bull. American Mus.Nat. Hist., 154(1):51 pp.Barr, T.C., Jr., and H.R. Steeves. 1963. Texamaurops, a newgenus of pselaphids from caves in central Texas (Coleoptera:Pselaphidae). Coleopterists Bull., 17:117-120.Brendel, E. 1893. Notes and descriptions of Pselaphidae, withremarks on the Scydmaenidae. Trans. American Entomol.Soc., 20:277-284.Casey, T.L. 1897. Coleopterological notices. VII. Ann. NewYork Acad. Sci., 9:285-684.Casey, T.L. 1908. Remarks on some new Pselaphidae. CanadianEntomol., 40:257- 281.Chambers, S.M., and S. Jahrsdoerfer. 1988. Endangered andthreatened wildlife and plants; final rule to determine fiveTexas cave invertebrates to be endangered species. FederalRegister, 53(180) :36029-36033.Chandler, D.S. 1985. The Euplectini of Arizona (Coleoptera:Pselaphidae). Entomography, 3:107-126.Chandler, D.S. 1988. A revision of the Nearctic genus Cylindrarclus(Coleoptera: Pselaphidae). Trans. American Entomol.Soc., 114:129-146.252