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has been Jiscussed by Segerstrom (1961) and Smith(1972). Karst development is represented by largedolinas, sinkholes, and lapiez. The Rio J alpan hasbeen captured by a large cave and now runs through anatural tunnel (known as Puente de Dios) for 1.5kilometers. Most of the caves are vertical pits, withthe Sotanito de Ahuacatlan attaining a depth of320 meters.This region has been little studied biologically;only nine caves have received attention. The onlytroglobite among the 17 species identified is thecixiid homopteran Cixius orcus Fennah. The troglophilefauna includes the diplurid spider Euagrusluteus Gertsch, a ctenid spider of the genus Ctenus,a pholcid spider of the genus Modisimus, a scytodidspider of the genus Loxosceles, a rhachodesmid millipedof the genus Strongylodesmus, campodeid diplurans,the gryllid cricket Paracophus placonotusHubbell, the carabid beetle Platynus acuminatus(Chevrolat), and a leiodid beetle of the genus Ptomaphagus(Adelops). All of these species are typicalof the cave fauna of the Sierra Madre Oriental to theeast.Laguna Colorado, Queretaro.-This region is thewestern extension of the karst region of Xilitla, SanLuis Potosi. All of the caves investigated are formedin the EI Abra (=EI Doctor) Limestone. Karst developmentis not as great as near Xilitla, but large shallowdolinas and numerous sinkholes occur. Bonet (1953a)has discussed the regional geology and physiographyand includes a map of the largest cave in the region,Cueva del Madrofio. The elevation of this cave is1,810 meters. The remaining four caves studied aresmall.The only two troglobites thus far recorded are the()pilionid Hoplobunus queretarius Silhavy and therhachodesmid milliped Unculabes arganoi Shear. Bothare closely related to other species in the Sierra MadreOriental. Although 29 other species have been recordedfrom the region, many are mites identifiedonly to family. The determined troglophile fauna includessuch typical elements of this general area asthe leptonetid spider Leptoneta sp., the pholcidspider Metagonia maximiliani Brignoli, the cleidogonidmilliped Cleidogona sp., the rhachodesmidmilliped Strongylodesmus sp., the collembolan Lepidocyrtussp., the gryllid cricket Paracophus placonotusHubbell, the carabid beetle Platynus (Mexisphodrus)sp., and the Iciodid beetle Ptomaphagus (Adelops)leo Peck.Pinal de Amoles, Queretaro.-This region is locatedimmediately west of the Ahuacatlan region and consistsof an extensive area of Cretaceous limestone ofthe El Abra (=EI Doctor) Formation. A geologicalmap of the region is included in Segerstrom (1961).Karst development includes many large dolinas,sinkholes, and lapiez. Most of the caves investigatedhave been rather small, but Sotano del Buque is1,149 meters long and attains a depth of 506 meters(Jefferys, 1979) Although 21 caves have beenstudied, the region remains largely unknown.A total of 46 species have been identified from thecaves of the region. Of these, six are troglobites: theagelenid spider Tegenaria caverna Gertsch, the leptonetidspider Leptoneta delicata Gertsch, the trichopetalidmilliped Mexiterpes metallicus Shear, therhachodesmid milliped Strongylodesmus sp., andthe carabid beetles Mexaphaenops elegans Barr andParatrechus (Hygroduvalius) pallescens Barr. All ofthese species are most closely related to species knownfrom other parts of the Sierra Madre Oriental. Troglophilesof interest include the diplurid spider Euagrusluteus Gertsch; an agelenid spider of the genus Tegenaria;a ctenid spider of the genus Ctenus; the nesticidspiders Eidmannella pallida (Emerton), Gaucelmusaugustinus Keyserling, and Nesticus vasquezaeGertsch; the pholcid spiders Coryssocnemis ivieiGertsch, C. simoni O. P.-Cambridge, and Physocyclusreddelli Gertsch; the scytodid spider Loxoscelesaranea Gertsch; the phalangodid harvestman Pellobunusmexicanus Goodnight and Goodnight; thecleidogonid millipeds Cleidogona mayapec Shearand C. totonaca Shear; a rhachodesmid milliped ofthe genus Strongylodesmus; the gryllid cricket Paracophusplaconotus Hubbell; the carabid beetlesPlatynus tlamayaensis (Barr) and P. (Mexisphodrus)sp.; and staphylinid beetles of the genera Belonuchusand Philonthus.San Joaquin, Queretaro.-This region is locatedsouth of the Pinal de Amoles region. The geology hasbeen studied by Wilson et al. (1955). All of the cavesknown are formed in the EI Abra (=EI Doctor) Limestone.Karst development includes dolinas, sinkholes,and lapiez. Much of the drainage is internal. The elevationis about 2,400 meters.This region remains essentially unstudied; onlythree caves have been investigated. Of the three specieswhich have been identified, two spiders are troglophiles:the pholcid Coryssocnemis simoni O. P.­Cambridge and an undescribed species of nesticid ofthe genus Nesticus.San Juan, Queretaro.-Only seven caves have beenbiologically examined in this region, which is locatednorth of the Ahuacatlan region. Stone and Jameson(1977) have published a comprehensive report on theregion, including descriptions of all caves and a generalstudy of the geology. All of the caves known are31