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Records.-Veracruz: Grutas de Atoyac, Cueva delOjo de Agua Grande, and Cueva de Sala de AguaGrande.Discus&on.-This species was abundant on andnear rotting wood in the wetter areas of each of thethree above caves.Family ParadoxosomatidaeTwo species of the family Paradoxosomatidae havebeen found in caves in Mexico, Guatemala, and Belize.Both are tropicopolitan in distribution and nowappear almost everywhere man is found. Oxidus gracilis(Koch), the hothouse milliped, has been collectedin 14 caves in Nuevo Leon, San Luis Potosi,Queretaro, Hidalgo, Veracruz, and Guerrero, Mexico;and from one cave in Belize. Orthomorpha coarctataSaussure has been found in Cueva Jobitzinaj, El Peten,Guatemala; and in caves in Oaxaca and Yucatan.Most of the caves inhabited by these two species areeither frequented by man or are in or near towns.Family PeridontodesmidaeThe peridontodesmid genera Hexodontin andPeridontodesmus have been collected from caves inSan Luis Potosi and Tamaulipas; their ecologicalstatus is unknown. A possibly undescribed genus andspecies of troglobite is known from two caves inChiapas.Family PyrgodesmidaeNo family which has invaded caves in Mexico andCentral America has been so prolific in the number ofspecies which have become established in caves as thePyrgodesmidae (=Stylodesmidae). Although 34 speciesin this family have been reported from caves andmost are known only from caves, this is only a smallpercentage of the number which eventually will bedescribed from the cave habitat. Numerous collectionsawait study, and despite the recent contributionof Shear (1977a), systematic problems still preventmany of these from correct identification orgeneric placement.Many epigean forms are poorly pigmented so thatit is presently not possible to list any of the speciesas restricted to caves. Some members of the familyhave certainly become sufficently distinct as to beisolated now in the cave environment, but only muchadditional study and a better understanding of thesystematics of the family will allow us to say whichspecies are troglobites and which troglophiles. Nicholas(1962) listed seven species from Mexico and onefrom Guatemala as troglobites; none of these appearto possess unusual modifications restricting them tocaves.These small millipeds are usually black, gray, orcream colored, and many species are covered with afine layer of dirt adhering to the numerous smallknobs and projections on the body. They are foundin a variety of habitats in caves, ranging from moistflowstone, guano, and silt to the underside of smallrocks and rotting wood.The genus Myrmecodesmus has recently beenexpanded by Shear (1977a) to include species previouslyplaced in the genera Bolivaresmus, Ceratesmus,Gibberdesmus, and Stenotodesmus. The followingis a list of the 18 species of cavernicole Myrmecodesmusknown from this area (see Figs. 55-56).Myrmecodesmus aconus (Shear, 1974)-Gruta de laEstrella, Guerrero, and Cueva de Coatepec, Mexico,Mexico.M. amarus (Causey, 1971b)-Sotano de Tlamaya, SanLuis Potosi, Mexico.M. amplus (Causey, 1973)-three caves near Valle Nacional,Oaxaca, Mexico.M. brevis Shear, 1977a-Rio Frio Cave A, Belize.M. clarus (Chamberlin, 1942)-Grutas de Atoyac andLas Tres Cuevas, Veracruz, Mexico.M. colotlipa (Chamberlin, 1942)-Grutas de J uxtlahuaca,Guerrero, Mexico.M. cornutus (Shear, 1974)-Cueva del acimiento delRio Frio, Tamaulipas, Mexico.M. egenus (Causey, 1971b)-caves in Tamaulipas,Mexico.M. errabundus (Shear, 1974)-caves in the northernSierra de EI Abra, Tamaulipas, Mexico.M. fissus (Causey, 1977a)-Sumidero del Camino,Chiapas-NEW COMBINATION.M. fuscus (Causey, 1977a)-Grutas de Atoyac andCueva de la Sala de Agua Grande, Veracruz, Mexico-NEWCOMBINATION.M. gelidus (Causey, 1971b)-caves in Tamaulipas,Mexico-NEW COMBINATION.M. ilymoides (Shear, 1974)-Grutas de San Bartolo,Nuevo Leon, Mexico.M. inornatus Shear, 1977a-Grutas de Llano Grande,Chiapas, Mexico.M. monasticus (Causey, 1971b)-Cueva de Llanura,San Luis Potosi, Mexico.M. potosinus (Shear, 1974)-Cueva de la Porra, SanLuis Potosi, Mexico.M. sabinus (Chamberlin, 1942)-caves in the southernSierra de EI Abra, San Luis Potosi, Mexico.M. unicorn Shear, 1977a-S1. Hermans Cave andMountain Cow Cave, Cayo District, Belize.The genus Calymmodesmus includes one speciesfrom Guatemala and five from Yucatan (see Fig. 57).180