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undescribed genus and species of chactid scorpion; asecond species of the same genus is known from thePurificacion region to the north. The troglophilefauna is typical of the general region and includes thecrayfish Procambarus (Ortmannicus) villalobosiHobbs, the amblypy¢d Paraphrynus pococki l\Iullinex.the ctenid spider Ctenus mitchelli Gertsch, thenesticid spiders Eidmannella pallida (Emerton) andGaucelmus augustinus Keyserling, the opilionidsKaros gratiosus Goodnight and Goodnight and K.projectus Goodnight and Goodnight, and the gryllidcricket Paracophus placonotus Hubbell.Sierra de Alvarez, San Luis Potosl.-This is one ofthe westernmost ranges of the Sierra Madre Orie~taland is located east of the city of San Luis PotosI.Karst development is considerablt~, with most drainagebeing subterranean. Karst forms include dolinas,sinking streams, lapiez, and pinnacles. The greatestdevelopment is in an area known as Valle de los Fantasmas,where numerous pinnacles brive an eerieappearance during times of fog. The caves arc formedin the El Abra (=El Doctor) Limestone. Cserna andBello-Barradas (1963) have studied the regionalgeology. Brief descriptions of the caves and a checklistof the fauna are in Elliott and Reddell (1973).There have been 26 caves investigated biologically;these range in elevation from 2,100 to 2,350 meters.This is one of the hetter-known regions in Mexicowith respect to its invertebrate cave fauna, with 95species having been identified. Of these, only two aretroglobites: the trichopetalid milliped JIJexiterpesegeo (Causey) and the trechine beetle Mexaphaenopsfishi Barr. Both belong to genera known from otherparts of the Sierra Madre Oriental. The rarity of troglobitesin this high altitude region is surprising, butmay be a reflection of greater aridity and less diverseflora. The troglophile fauna is also typical of theSierra Madre Oriental. It includes the tarantulaSchizopelma elliotti Gertsch; the agelenid spiderTegenaria selva Roth; the mysmenid spider Maymenachica Gertsch; the nesticid spider Eidmannella pallida(Emerton); the pholcid spiders Coryssocnemis abernathyiGertsch, Metagonia punctata Gertsch, andPsilochorus concinnus Gertsch; the opilionids Cynortajamesoni Goodnight and Goodnight and Karosparous Goodnight and Goodnight; millipeds of thegenera Myrmecodesmus, Strongylodesmus, and Tiphallus;the collembolan Pseudosinella reddelliChristiansen: and carabid beetles of the generaBembidion, Platynus, and Platynus (Mexisphodrus).Sierra EI Pino, San Luis Potosi.-This region is amountain range east of Ciudad del Maiz with elevationsfrom about 1,100 to 1,900 meters. The regionremains poorly knvwn, and only six caves have beenvisited. Large sinkholes are known on top of therange but are unvisited. Water falling on the westernside of the range drains into a closed lake or intocaves located in a wide, shallow arroyo. Two of thesecaves and a few on the slopes of the mountain havebeen studied.The fauna of the region includes two aquatic andthree terrestrial troglobites: the entocytherid ostracodSphaeromicola cirolanae Rioja, the cirolanidisopod Speocirolana pelaezi (Bolivar), a trichopolydesmidmilliped, the collembolan Pseudosinellapetrustrinatii Christiansen. and the gryllid cricketParacophus lippus Hubbell. All are typical representativesof the fauna of the Sierra Madre Oriental.The troglophile fauna includes the ctenid spiderCtenus mitchelli Gertsch, the gryllid cricket Paracophusn. sp., the scydmaenid beetle Euconnus(Napochus) sp., the scarabaeid beetle Onthoplwguscuevensis II owden, and staphylinid beetles of thegenus Belonuchus.Xilitla, San Luis Potosi.-The Xilitla region is oneof the great karst regions in ~orth America. l\lassivereef deposits of Cretaceous EI Ahra (=EI Doctor)Limestone are highly cavernous, and numerous majorcaves and pits ex ist in the region. As considered inthis report, the region ex tends west from the easternface of the Sierra Madre Oriental to near the SanLuis Potosi-Queretaro border just past the town ofAhuacatLin. It is bordered on the north by the hill:hXilitla Plateau, on the west by the Laguna Coloradoregion, and on the south by the Rio .\Ioctezuma.Elevations range from about 100 to ahout 1,200meters. Much of the drainage is subterranean, withwater emerging from large springs, sOlTle vauclusian innature, along the east face of the range. Karst developmentis frequently intense with large dolinas, sinkholes,lapiez, and pinnacles present. Although severallarge caves exist, drainage does not appear to he ashighly integrated as in the Purificacion region, and nosystems to rival that of the Sistema Puri ficaciilll arclikely. In addition to numerous vertical shafts, somemore than 100 meters in depth, large chambers andvertical cave systems exist. Among the more importantcaves are Sotano de Huitzmolotitla with morethan three kilometers of passage and Sotano de rlamayawith a vertical depth of about -t.00 meters.Carrasco (1970) has discussed the stratigraphy of thegeneral area and concluded that the name El Ahrashould be applied to the limestone of the area. Ronet(1953a) has discussed the geology and physiography,and includes maps and descriptions of many of thecaves. Russell and Raines (1967) add infonnation ongeology and descnbe additional caves.34