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183(depigmented)1 and has the eyes reduced to tinYI pale spots.About 15 specimens have been collected in 25 yearsl apparentlyall of them from or quite near the entrance room of the cave.Two additional species of Mexaphaeno~sl not yet describedlhave been discovered by John Fish in the6tano de TeJamanil (Qro.)and in a small cave in Valle de los Fantasmos (S.L.P.). The occurrenceof all three of these species in caves at relatively highelevations is noteworthy. There is considerable evidence that thetroglobitic trechines of Europe and the United States are descendantsof boreal forest species which were widespread during periodsof glacial advance during the Pleistocenel but were able to survivethe warm, dry climate of the interglacials only by retreating intocaves where they underwent regressive evolutionary modificationsincidental to adaptation to the cave environment. Absence of troglobitictrechines (and troglobites of most other groups whichlive in humus and moss carpets) from tropical regions is attributedto the "isothermal" climatic conditions of the tropics. In otherwordS,. there were no major climatic changes which changed the surface(SOil and moss) environment to such an extent that surfacemembers of troglophUe species became extinct and the cave popUlationsthus became isolated in caves and developed into troglobites.The climate of Mexico, particularly the northern portions and thehigher elevations, was certainly much colder and wetter duringglacial maxima than it is today. It will be most surprising if aspecies of Mexaphaenops turns up outside of a high mountainousregion.In European trechinesl Jeannel was able to point to gradedseries of species which probably illustrate the stages from a surfacespecies (eyes, wings, pigment) to a cave species (troglobite).In the genus Duvalius, particularly, there are species which liveunder stones in the mountains and have small eyes, often elongatebody parts, and reduced pigment. There are even eyeless specieswhich live deep in humus in the mountains and resemble cave species.Bolivar's earlier discovery of Paratrechus sylvaticus, a pale, depigmentedspecies with small eyes, in Morelos and Distrito Federal,seem to provide a "missing link" in the construction of the samesort of ~raded series between typical Paratrechus and Mexaphaenopsprietoi s lAnales Esc. Cien. BioI., 2: 111-1181 pl. 9, 1941). P.1vaticus was p1aced-rn-a new-subgenus, ~grOdUValius, but tned1agnostic characters which Bolivar cited n 1941 have since beencalled into question by the description of other Paratrechus spp.,and it is now doubtful that P. sylvaticus is distinct enough towarrant subgeneric separation from other Paratrechus. The latest"link" in the series was forged with the discovery of a blinds2ecies of Paratrechusl closely related to P. h!lvaticus, in thes3tano de Tejamani1 (Qro.) by John Fish. r:n t s species, stillundescribed, the eyes are very small, palel and non-functional,but the body parts are not slender and elongate as in Mexaphaenops.It seems likely that Mexaphae~s includes the relicts or a mucholder invasion of the caves t this newly descovered species ofParatrechus. For the future, the biological exploration of Mexicancaves at the higher elevations should prove most interestingl particularlyas additional species of troglobitic trechines show up.The agonine carabids include the genera Rhadine and Mexisphodrus,as well as Agonuml ClIE~~isl and a few other genera collectedrn-Mexican caves. No trog 0 c Rhadine have been found in Mexico.The genus is rather widely distributed in Western North America,