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generally more dissected than in Chiapas. Numerouscaves are known in the Chiapa Depression, mostly inthe vicinities of Tuxtla Gutierrez, Ocozocoautla, andMalpaso.The central plateau of Chiapas is among the greatkarst regions in Mexico. The plateau rises steeplyfrom the Chiapa Depression to an elevation of about2,300 meters. Parts of the plateau, such as near SanCristobal de las Casas, are rolling plains with numerousshallow dolinas. In other areas there is the greatestdevelopment of karst in Mexico, with sinkholes,dolinas, poljes, and sinking streams occurring everywhereon the Cretaceous limestone surface. This isthe best-studied part of Chiapas; 48 caves have beenstudied biologically. This surface continues on alesser scale into the Altos Cuchumatanes of Guatemalawhich attains an altitude of more than 3,000meters. Farther east in Alta Verapaz the topographyis more rugged; and in the vicinity of Coban, it isbroken into three parallel mountain ranges separatedby basins. Karst development in this area is notable,with large caves, dolinas, sinking streams, and othersolution features being abundant.The northern side of the plateau is composed of aseries of folded ranges in Cretaceous and Tertiaryrocks. As the ranges pass into Guatemala, theydecrease in heigh l until they are hills in the sou themPeten. In Belize the land rises in the Maya Mountains,where intrusive rocks and Pennsylvanian and olderdeposits are exposed. Limestones of Cretaceous toEocene age are exposed to the north, south, and westof the Maya \10untains and support a mature karsttopography.Altamirano, Chiapas.-This region is located nearthe towns of Altamirano and Ocosingo in the foldedmountains north of the high plateau. Eight caves havebeen studied, seven of which are described by Sbordoniet al. (1977). The caves are generally horizontaland at least one, Sumidero de Panteon, receives considerablefloodwater.The caves appear to be quite rich biologically, butlittle has been published on them to date. Of 16species thus far reported, four are troglobites. Threeof the troglobites are aquatic and include the asellidisopod Caecidotea vomeroi Argano and the bogidiellidamphipods Bogidiella sbordonii Ruffo and VignaTaglianti and B. tabascensis Villalobos. The last speciesis also known from Grutas del Cocona nearTeapa, Tabasco. The only terrestrial troglobite is anundescribed roach of the genus Nelipophygus. This isthe only tro~lobitic roach in Mexico; the genus isotherwise known from Jamaica where a troglobiticspecies also occurs. The troglophile fauna includes theamphipod Hyalella azteca Saussure, the ochyroceratidspider Ochyrocera fagei Brignoli, the oonopid spiderOonops chickering; Brignoli, the pholcid spiderCoryssocnemis pecki Gertsch, and the roach Nesomylacrislateralis Fisk. Except for the Widespreadamphipod H. azteca and the spider C. pecki, all ofthe troglophiles are endemic to this region. The latterspecies is also known from caves in the San Cristobalde las Casas region.Bochil and Soyalo, Chiapas.-This region is locatedto the northwest of San Cristobal de las Casas. Thesix caves studied occur at elevations ranging from1,250 to 1,600 meters and are described by Sbordoniet aI. (1974, 1977). Several of the caves are ratherlarge and generally horizontal. Sumidero del Naranjoreceives some floodwater, and Cueva del Nacimientodel Rio Santo Domingo contains a large stream.Although most of the cave fauna remains to bereported on, 16 species have been identified, of whichthree are troglobites. The troglobites are the opilionidTroglostygnopsis anophthalma Silhavy, the glomeridesmidmilliped Glomeridesmus ?sbordonii Shear,and the trichopolydesmid milliped Caramba delnegroShear. The opilionid and trichopolydesmid millipedare endemic to the region, but G. sbordonii is alsoknown from Grutas del Cocona, Tabasco. The troglophilefauna includes the crayfish Procambarus (Austrocambarus)sbordonii Hobbs, the schizomid Schizomusarganoi Brignoli, the mysmenid spider Maymenamayana (Chamberlin and Ivie), the nesticidspider Eidmannella pallida (Emerton), the pyrgodesmidmilliped Synoptura italolegata (Shear), thesphaeriodesmid millipeds Sphaeriodesmus golondrinensisShear and S. redondo Shear, the roach Aglaopteryxchiapas Fisk, and a species of leiodid beetleof the genus Ptomaphagus (Adelops). With the exceptionof the two spiders and the milliped S. italolegataall of these species are endemic to the region. The spidersare widespread in southern Mexico and S. italolegatais also known from other parts of Chiapas eastinto the Yucatan Peninsula.Comitim de Dominguez, Chiapas.-This region islocated in the vicnity of the town of Comitan deDominguez in eastern Chiapas. The principal cavernousformation in the region is the Sierra MadreLimestone of Cretaceous age (Gu tierrez Gil, 1956).Only two caves have been studied in this area, thelargest of which is Cueva del Tio Ticho (Sbordoniet al., 1974). This cave is a sinkhole about 60 metersdeep, with a stream at the bottom. The other cave issmall and of little interest. Both caves are located atan altitude of about 1,700 meters.The fauna of the region is of considerable interestand further study should greatly increase the numberof species known. Of the 25 species recorded, five are47