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igneous rock immediately east of the Sierra de Guatemala.In the shallow valley separating this ridge andthe main range, several caves receive floodwater viashallow arroyos. These caves are largely vertical andattain depths up to 148 meters below their entrances.Water has been encountered in three of these (Mitchellet al., 1977). Karst development in the Sierra deGuatemala includes numerous dolinas, pinnacles,lapiez, and sinkholes. A few small springs emerge toflow short distances before sinking. Most of the exploredcaves on or near the top of the range are smallsinkholes ranging from a few meters to more than100 meters in depth. Several large chambers and phreaticallyformed passages have been encountered; themost notable of these are Cueva de la Mina, Cueva dela Capilla, and Cueva del InfierniIlo. These welldecoratedcaves usually have permanent pools ofstanding water, occasionally inhabited by aquatictroglobites. Elliott (1973b) has included descriptionsof several caves in the area. Along the northern edgeof the Sierra de Guatemala several significant caveshave been discovered. These include long, horizontalcaves which may represent fossil resurgences. Thelargest cave in the range is Sotano de la Joya de Salas,located on the western side of the range in a largeclosed valley. The cave receives massive amounts ofwet-season floodwater and attains a depth of 376meters. In general, karst development in the Sierrade Guatemala appears to be in a rather early stageand it appears doubtful that a major cave system,such as the Sistema Purificacion, will be found.The Sierra de Guatemala is among the betterknownareas in Mexico with respect to its invertebratefauna. From the 67 caves which have beenstudied, 273 species, including 45 troglobites, areknown. This is largely a reflection of the great rangein elevation and the variety of habitats. The aquatictroglobite fauna includes two flatworms, Dugesiabarbarae Mitchell and Kawakatsu and D. typhlomexicanaMitchell and Kawakatsu. These are closelyrelated to the troglophile D. guatemalensis Mitchelland Kawakatsu, also known from caves in the region.The aquatic earthworm Eodrilus albidus Gates hasbeen found in pools in two caves; it is closely relatedto the troglobitic E. mexicanus Gates from the XiIitiaregion. The microcerberid isopod Mexicerberus troglodytesSchultz is a marine relict known only fromCueva de la Mina. Its affinities are unclear. The remainingaquatic troglobites are also known fromcaves in the Sierra de EI Abra. These are the entocytheridostracod Sphaeromicola cirolanae Rioja, thecirolanid isopods Speocirolana bolivari (Rioja) andS. pelaezi (Bolivar), and the characin Astyanax jordani(Hubbs and Innes). The last species is knownfrom caves at Gomez Farias and from the areaimmediately to the north of Ocampo along thesouthern edge of the range.The terrestrial troglobite fauna is the richest ofany region in Mexico and includes a wide variety ofspecies. Most of the species are endemic, but severalare also known from the Sierra de El Abra and oneoccurs to the north. The collembolan Oncopoduraprietoi Bonet was described from Grutas del Palmitoin the Sierra de Gomas. Six species are also knownfrom caves in the Sierra de El Abra: the squamiferidisopod Spherarmadillo cavernicola Mulaik, the trichoniscidisopod Brackenridgin bridgesi (Van Name), theamblypygid Paraphrynus baeops Mullinex, the opilionidHoplobunus boneti (Goodnight and Goodnight),the centipede Newportia sabina Chamberlin,and the collembolan Pseudosinella petrustrinatiiChristiansen. Of the remaining fauna some speciesare known from both high and low elevations, whileothers may be restricted to either highland or lowlandcaves. Species which are known from all elevationsare the glomerid miIIiped Glomeroides promiscusCausey, the rhachodesmid milliped Strongylodesmusharrisoni Causey, the opilionid Hoplobunusinops Goodnight and Goodnight, and the gryllidcricket Paracophus caecus Hubbell. The cambalidmilliped Mexicambala blanda Causey is known bothfrom medium and low elevations, while its siblingspecies M. inops Causey occurs at higher elevations.Species which are apparently restricted to low elevationsinclude the pseudoscorpion Paravachoniumsuperbum Muchmore, the schizomid Schizomusreddelli Rowland, the ochyroceratid spider Theotimapura Gertsch, the trichopolydesmid milliped Tylogoneusminus Causey, and the histerid beetles Troglobacaniusreddelli Vomero and T. sbordonii Vomero.Of these species all bu t the milliped are probablytropical forms not likely to occur at higher elevations.The nearest relative of the milliped occurs inthe Xilitla region and thus it may also be found athigher elevations.The high-elevation fauna is of particular interest.It includes the chactid scorpion Typhlochactas rhodesiMitchell, the pseudoscorpions Aphrastochthoniusmajor Muchmore and Tyrannochthonius troglobiusMuchmore, the diplurid spider Euagrus cavernicolaGertsch, the agelenid spiders Cicurina (Cicurusta)mina Gertsch and Tegenaria blanda Gertsch, the leptonetidspider Leptoneta capilla Gertsch, the pholcidspider Metagonia pura Gertsch, the palpatorid opilionidOrtholasma sbordonii Silhavy, the cleidogonidmilliped Cleidogona pecki Shear, the rhachodesmidmiIIiped Unculabes causeyae Shear, a trichopolydesmidmilliped possibly belonging to the genus37