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at sites that are latitudinally in the Neotropics or the transition zone 
between the two biogeographic regions. In the Parajulidae, Causey 
(1974) reported that Mexican forms occur in the temperate zone near 
the coast but are absent from the “tierra caliente” lowlands; they are 
most abundant on the plateau and follow the mountains southward 
into western Guatemala, where they are restricted to the mountains. 
Likewise in the Spirobolidae, Hiltonius Chamberlin extends southward 
from southern Arizona to southwestern Guatemala, where forms occur 
only “in high mountainous regions” (Keeton 1960). Finally, Sakophallus 
simplex Chamberlin, a species with west-Nearctic affinities provisionally 
assigned to the Nearctodesmidae, is known only from high elevations 
in western Jalisco and Michoacan (Shelley 1994 a). 
The Xystodesmidae, Nearctodesmidae, and Glomeridae also exhibit 
substantial Mexico/United States range disjunctions (Table 6). The 
degree of continuity is unknown in the Parajulidae, which has never 
been comprehensively studied at the generic and specific levels, and 
although Keeton (1960) revised Hiltonius, enough new material exists 
in American repositories to reassess the Mexican forms, which range 
northward into Santa Cruz County and adjacent parts of southern Arizona. 
A hiatus appears to exist between southern Arizona and coastal California, 
and there may or may not be one in Mexico. The Mexican representatives 
of the Xystodesmidae, Rhysodesmus Cook and Stenodesmus Saussure, 
also occur in the adjacent fringe of the United States, and there is 
a sizeable lacuna between them and the east-Nearctic species, the 
most proximate localities being in the lower Rio Grande Valley of 
Texas and northern Louisiana (Hoffman and Shear 1964, Hoffman 
1970, Shelley 1987). 1 An even larger gap exists between the most 
proximate sites of Sakophallus Chamberlin, in Jalisco, and Nearctodes- 
mus Silvestri, in Marin County, California (Shelleyl994fl). Regarding 
Glomeroides, the only United States species, G. prima (Silvestri), occurs 
in the San Francisco Bay area. The type locality is in Marin County; 
Shear (1986) reported Pfeiffer Big Sur State Park, Monterey County; 
and I now add Redwood Regional Park, Contra Costa/Alameda counties, 
based on juveniles collected on 18 May 1953 by R. O. Schuster and 
E. E. Gilbert (NMNH). 
1 The Louisiana species is Boraria profuga (Causey), known previously only from the 
type locality in Montgomery County, Arkansas, in the Ozark-Ouachita Physiographic 
Province. The Louisiana locality, in the Gulf Coastal Plain, is Monroe, Ouachita County, 
based on unreported males and females collected in December 1974 and 1978 by 
M. R. Cooper (NCSM). 
