xx INTRODUCTION. 
regions, being especially well represented in Europe, North America, South Africa, 
and Australia. Prostenus, Xystropus, Lystronychus, Cteisa, and Lobopoda are charac- 
teristic of the tropical regions of America—and all are represented in the Central- 
American fauna, the last-mentioned by forty-six species; and Hymenorus and Cistela 
of the more northern portion of the American continent. Twelve genera are known 
only as yet from within the limits of Central America, seven of which are peculiar 
to Mexico, two to Guatemala, and one to the State of Panama. It is probable, 
therefore, that Mexico contains at least four or five endemic genera of this family. 
Of the new genera described, Diopwnus, Manes, Phedius, and Erxias are the most 
interesting ; Phedius, with nine representatives in Mexico, is apterous or nearly so, 
and its species live beneath stones on the ground. The males of the Lobopod@ have 
the genitalia highly chitinized and complex, and these organs afford excellent corrobo- 
rative specific. characters, as will be seen from our Plates XVII. and XVIII. 
Hymenorus is one of the most perplexing genera of the family, its species being very 
numerous and closely allied. 
The family Othniide is limited to a single genus, Othnius (= Elacatis, Pascoe) ; 
six species occur in Central America, of which five are described as new. The genus 
is a very widely-distributed one, occurring in Borneo, New Guinea, Ceylon, Japan, and 
North and Central America, but with no known representative as yet from the South 
American continent. Its species are of active, predatory habits, and they are usually 
found running on the bark of fallen trees in search of food. 
The family Nilionide, in its true sense limited to the one genus Wilio, is confined to 
‘Tropical America. It contains numerous species in South America, but has only four 
representatives—three of which are described as new—within our limits, where it 
ranges as far north as the Mexican State of Vera Cruz. Its species greatly resemble 
various Endomychide and Coccinellide; they are found about fungoid growth on 
trees and are very sluggish in their movements. 
The family Monommide, formerly placed in the Serricornia between the Throscidse 
and the Eucnemide, is remarkable from the compact form of the exoskeleton of its 
various species, resembling in this respect the Throscide and the Histeride. Three 
genera only are known as yet—one, Monomma, confined to the warmer parts of the Old 
World; the other two, Hyporhagus and Aspathines, exclusively American, Aspathines 
