458 PROCEEDESTGS OF THE NATIONAL MUSEUM vol. xii 



northern subgenus, which contains the type of " Homalojxjrus" and 

 so must take that name, has the evaporatorium very restricted, it 

 being separated from the posterolateral angle of the sclerite by the 

 polished lateral area (fig. 103). Subgenus Homalojwrus, in most of 

 its species, has more setigerous punctures laterally than does nominal 

 Pangaeus. In the former subgenus all species except rugiceps bear 

 two or more submarginal setigerous punctures distad of the preocular 

 one; and normally have two or more costal setigerous punctures. In 

 nominal Pangaeus all but four closely allied species of the dozen 

 included forms have no setigerous punctures distad of the preocular 

 one, and, with four exceptions, the number of costal setigerous punc- 

 tures is usually one or two with only an occasional specimen showing 

 three — the exceptions being suhtilius, xanthopus, jjluripunctatus , new 

 species, and semibrunneus, new species, each of which has five to ten 

 such costal punctures. 



The shape of the mesopleural evaporatorium alone furnishes the 

 most reliable feature for separating these subgenera and permits the 

 forming of the following couplet: 



Key to subgenera of Pangaeus 



1. Mesopleural evaporatorium extending uninterrupted alone: posterior margin 

 of sclerite into posterolateral angle (fig. 103) Pangaeus (Pangaeus) (p. 477) 

 Mesopleural evaporatorium limited, separated from posterolateral angle and 

 posterior margin of sclerite by polished area (figs. 102, 104). 



Pangaeus (Homaloporus) (p. 458) 



Subgenus Pangaeus (Homaloporus) Uhler, new status 



Diagnosis. — The hmited mesopleural evaporatorium (figs. 102, 

 104), which does not reach into the posterolateral angle of the segment, 

 sets this subgenus apart from the nominal subgenus. 



Description. — The generic description as modified by the notes 

 in the generic discussion will furnish suflicient characterization for 

 this subgenus. 



Type of subgenus. — Homalojwrus congruus Uhler, monobasic. 



Distribution. — This subgenus occupies the northern part of the 

 range of the genus from Guatemala north into the United States, where 

 it is known to occur as far north as Nev/ York, Iowa, and Nebraska 

 east of the Great Plains and west from Texas across New Mexico 

 and Arizona into southern California. 



Discussion. — Pangaeus rugicejJS Horvdth might be considered 

 somewhat intermediate between this subgenus and the nominal one 

 on the basis of the reduction of the number of setigerous punctures on 

 the submargin of the head and costa. However, the shape of the 

 mesopleural evaporatorium, which the author considers a better 

 phylogenetic indicator, clearly places it in the subgenus Homaloporus. 



