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Temperate relicts.-A few species of troglobite areknown from Mexican caves which belong to groupsunknown from the surface in this region. These includethe centipede Nuevobius cavieolens Chamberlin,millipeds of the families Cambalidae and Trichopetalidae,and collembolans of the genera Acherontidesand Oneopodura. In our present state of knowledgeof the endogean fauna of tropical and subtropicalregions, we can only speculate that thesegroups will not be found on the surface. It wouldappear, however, that they represent true relicts of afauna once widespread throughout Mexico but nowto be found only in caves.The centipede Nuevobius cavieolens Chamberlinis known only from Cueva de la Boca in the Sierra dela Silla, Nuevo Leon. The only other species in theI!tnus is a trog/obite from Tennessee (U.S.A.).The rnilliped families Cambalidae and Trichopetalidaeare unknown on the surface in Mexico orCentral America. It is likely that these species aresurvivor;; of a once-widespread fauna inhabiting thetemperate forests that once covered parts of thisregion. These forests are now represented only byrelict poekeb at higher elevations of the Chiapas­Guatemalan Highlands, Sierra Madre del Sur, andSierra :\1adre Oriental.The family Camhalidae is an important element ofthe cave and endogean fauna of the United States.One aberrant species, larmilka alba Shear, is knownonly from a cave in Belize. The genus lvlexicambalaincludes described species from caves in Oaxaca, SanLuis Potosi, and Tamaulipas. It is probably a relictof a group once widespread in Mexico hut that isnow restricted to caves. Finally, Cambala speobia(Chamberlin) has been collected in Cueva de losLagos, Coahuila. This is a common species in thecaves of Central Texas immediately north of the RioGrande.The family Trichopetalidae is a significant group inthe cave and endogean habitats of the southeasternUnited States. In Mexico it is represented only by thegenus Mexiterpes with four troglobitic species fromcaves in San Luis Potosi and Queretaro. The mosthighly cave-adapted species (M. sabinus Causey)occurs at comparatively low elevations in the Sierrade El Abra. The remaining species, which occur atmuch higher elevations, retain ocelli and are apparentlymore recent troglobites. It would appear thatthese were inhabitants of a temperate forest whichbecame extinct earlier at lower elevations than athigher ones.Two genera of collembolans appear to be temperaterelicts in the caves of Mexico. The hypogastruridgenus Acherontides is known only from two Mexicancaves, A. atoyaeense Bonet in Veracruz and A. potosinusBonet in the Xilitia region of San Luis Potosi.Other species of the genus occur in Rumania, Japan,and Afghanistan. The oncopodurid genus Oncopoduraincludes O. atoyaeense Bonet from Veracruz andO. prietoi Bonet from Nuevo Leon and possiblyTamaulipas. Other species of the genus occur inEurope, Japan, and the United States.There are several other groups which are unknownfrom the epigean habitat in Mexico but include troglobites.Among the more important of these are sixdescribed and several undescribed millipeds of thefamily Trichopolydesmidae, agelenid spiders of thegenus Cieurina, and ptinid beetles of the genus Niptus.It is likely, however, that as the endogean faunaof Mexico becomes better known these groups willalso be found in surface habitats.The family Trichopolydesmidae is known from theepigeum in Mexico only by two species in BajaCalifornia. All of the remaining species are troglobites.These are divided among three genera, Carambawith three species in Chiapas, Speodesmus with onespecies in Tamaulipas, and Tylogoneus with twospecies in San Luis Potosi and Tamaulipas. Each ofthese species is known only from the type-locality.The spider genus Cicurina is a major element ofthe cave and epigean fauna of Texas and other par.tsof the United States. In Mexico three troglobites andone troglophile have been described. The troglobitesare known from caves in Yucatan, Tamaulipas, andCoahuila, and the troglophile from caves in Tamaulipas.With more collections from high elevations inMexieo, this genus will almost certainly be found inendogean habitats.Two species of beetle of the family Ptinidae areknown from ;\1exican caves: Niptus abseonditusSpilman, a possible troglobite from Hidalgo, and N.abstrusus Spilman, a troglophile from caves in Texas(U.S.A.) and Coahuila and Durango, Mexico. Neitherspecies has been collected from the surface, but it islikely that N. abstrusus or other species of the genuswill be found there with more collecting.Species with temperate affinities.-Several groupsof cavernicole are members of genera containing bothepigean and cavernicole species, but which havecloser affinities to temperate species than to speciesinhabiting Mexico. These include trichoniscid isopodsof the genus Braekenridgia, scorpions of the genusTyphloehaetas, pseudoscorpions of the genus Aphrastochthonius,and spiders of the genera Tegenaria,Leptoneta, and Nestieus.The isopods of the genus Brackenridgia are amongthe most commonly collected animals in the caves ofMexico. Although only five species have thus far been63