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y volcanic deposits prevented the development of arich troglobitic fauna. The troglobites known fromthe region include the pseudoscorpion Albiorix bolivariBeier, an undescribed species of the schizomidgenus Schizomus, the opiIionid Caecoa arganoi Silhav)',the rhachodesmid milliped Ceuthauxus constansCausey, the thysanuran Anelpistina anophthalma(Bilimek), and the collembolan Spelaeogastruraguerrerense Bonet. Two copepods, Macrocyclopsalbidus (J urine) and Mesocyclops sp. ne. brazilianusKiefer, are the only probable aquatic troglophiles.The terrestrial troglophile fauna is closely allied withthe cavemicole fauna of southern Mexico, but severalspecies are known only from the caves of this region.These include the pseudoscorpion Lechytia cavicolaMuchmore; the pholcid spiders Physocyclus modestusGertsch, Psilochorus cordatus (Bilimek), and Psilochorustellezi Gertsch; the ricinuleid Cryptocellusboneti Bolivar; the opilionid Cynortina minutus(Goodnight and Goodnight); the pyrgodesmid millipedMyrmecodesmus acona (Shear); and the carahidbeetIe Tachys (Tacltyura) un is triatus (Bilimek).Other troglophiles of interest include the armadillidisopods Venezillo cacaltuamilpensis (Bilimek) andV. osorioi (Mulaik), the amblypygid Paraphrynusmexicanus (Bilimek), the agelenid spider Tegenariamexicana Roth, the mysmenid spider Maymenamistica Gertsch, the scytodid spiders Loxoscelesboneti Gertsch and L. misteca Gertsch, the carabidbeetles Paratrechus (Paratrecltus) tepoztlanensis Bolivarand Platynus (Stenoplatynus) umbripennis(Casey), the leiodid beetle Ptomapltagus (A delops)spelaeus (BiIimek), and the scarabaeid beetle Onthophagusvespertilio Howden, Cartwright, and Halffter.Acatlan, Oaxaca.-This region includes a series ofmountain ranges located near the town of Acatlimin ex treme northern Oaxaca. The principal cavernousformation is the Escamela Limestone of Cretaceousage (Lozano Romen, 1955). The mountainsarise abruptly from an alluvial plain on which sugarcaneis grown. No caves have yet been visited on thehigh slopes or tops of the ranges where pits andsumideros are reported to occur.. ;umerous cavesexist on the slopes of the mountains, and severalsizable streams emerge from cave entrances at thebase of the ranges. One stream now utilizes themain passage in Cueva de Juan Sanchez for morethan a kilometer (Byrd, 1976). Other notable cavesin the area include Cueva de la Finca, Cueva deLaguna Verde, Cueva de las Maravillas, and Cuevadel Nacimiento del Rio San Antonio, each of whichcontains several kilometers of passage.The cavemicole fauna of this still poorly studiedregion is among the richer in Mexico. From the 21caves biologically investigated, 91 species, of which25 are troglobites, have thus far been identified. Theregion is particularly rich in aquatic troglobites withseven species known: the mysids Spelaeomysis olivaeBowman and Antromysis (Antromysis) reddelliBowman, the a1pheid shrimp Alpheopsis stygicolaHobbs, the palaemonid shrimps iYlacrobrachium n. sp.and M. villalobosi Hobbs, the crayfish Procambarus(Austrocambarus) oaxacae reddelli Hobbs, and anundescribed species of catfish of the genus Rhamdia.The mysids and alpheid shrimp are presumablymarine relicts, while the other species probably havea freshwater origin. With the exception of A. stygicola,which is otherwise unknown from fresh water inthe New World, the remaining species are all closelyrelated to the fauna of southern lVlexico. The terrestrialtroglobite fauna includes the diplocentrid scorpionDiplocentrus cueva Francke, an undescribedspecies of pseudoscorpion of the genus Tyrannochthonius,the schizomid Schizomus ?firstmani Rowland,an amblypygid of the genus Paraphrynus, thetarantula Schizopelma reddelli Gertsch, the pholcidspiders Metagonia martha Gertsch and Pholcophoran. spp., the cyphophthallllid opilionid Neogoveamexasca Shear, an undescribed opilionid of the genusHoplobunus, undescribed millipeds of the familiesOniscodesmidae and Trichopolydeslllidae, an undescribedthysanuran of the family \icoletiidae,collembolans of the subfamily I'aronellinae and thegenera Pseudosinella and .-lcherontides, and an undescribedcixiid hOlllopteran.The troglophile fauna has not, for the most part,undergone systematic study, bu t a few species havebeen identified. These include the schizolllid Schizomusportoricensis (Chamberlin). the amblypygidParaphrynus aztecus (Pocock), dl'~ rnysmenid spidersJ-Jaymena delicata Gertsch and M. mayana (Chamberlinand Ivie), and the leiodid beetles Dissochaetllshetschkoi Reitter and Ptomaphagus (A delops) reddelliPeck. In addition to these species many undeterminedor undescribed troglophiles are known. Among themore significant of these are scorpions of the genusVaejovis, pseudoscorpions of the genera Albiorixand Tyrannochtltonius, diplurid spiders of the genusEuagrus, ctenid spiders of the genus Ctenus, pholcidspiders of the genus Pholcophora, scytodid spiders ofthe genus Loxosceles, pyrgodesmid millipeds of thegenus IHyrmecodesmus, eampodeid diplurans, leiodidbeetles of the genus Proptomaphaginus, scydmaenidbeetles of the genera Euconnus (Napochus) and Scydmaenus,and staphylinid beetles of the genus Belonuchus.Both the troglophile and troglobi te faunas ofthe Acatlan region are typical of the cavernicolefauna of other parts of southern Mexico. The only42