392 BtTLLETTN 63, UNITED STATES NATIONAL MUSEUM. 



It is also iit variance in Bhtpyl'tx, and rather th.m create another sub- 

 genus it is best to do as I have done and retain it as a section in the 

 present aggregate. 



Tibialis, pJaiiipenfiis. and schwcu-zii are all disturbing elements in 

 the subgenera in which they are jDlaced, and their true position in all 

 probabilit}' will only be known when the Mexican species shall have 

 been carefully studied. 



The genital characters give the essential definition to the present 

 subgenus : 



Male. — ^Apicale of the edeagophore more or less equilaterally tri- 

 angular, more or less depressed, apex not in the least attenuate, the 

 dorsal surface with a broad central membrano-chitinous area. In 

 sehu'ciTzn a well-developed groove is present and the apex attenuate. 



/^em«?t?.— Genital segment more or less triangular; apex chitinous, 

 flattened, and moderately produced, but narrow and evenly rounded 

 at tip, convex above and concave beneath. Dorsal plates of* the 

 valves oblong Avith the external edge converging ai)ically, angle not 

 evident. Appendage small and mammilliform, penicillate. Superior 

 pudendal membrane rather broadly exposed and reaching to the 

 ai)ical fourth of the dorsal plate. Genital fissure nearly closed. 



In scliwarzii the female characters are as discordant here as else- 

 where. 



Distrihution. — Of the three species and two races constituting the 

 present subgeneric aggregate, nigrina has the most extensive distribu- 

 tion, occurring in Oregon, Washington, Northern California, Nevada, 

 Arizona, Colorado, New Mexico, Nebraska, Kansas, Idaho, and the 

 Dakotas. It is to be inferred that it occurs in the intervening States 

 not mentioned above, but representatives are not at hand. 



DissimUis appears to be abundant in Arizona. It also occurs in 

 New Mexico. 



Xcradetisis, in Nevada, southward into Arizona and the Colorado 

 Desert of eastern southern California. 



Pei'longa is only known to me from Wyoming. 



Schwarzii occurs in Washington. It will be observed that Meta- 

 hlapylis onlj'' occurs in (\ilifornia within its northern and eastern 

 confines. Closely related species are undoubtedly jilentiful to the 

 southward in Mexico. 



Geiiedlogy. — Very little can be expressed in regai'd to the origin of 

 the species enumerated above. Too little is known of xcliwarzil; 

 7('t(/rina and (Jixsihuilis without doubt arose from a common ancestral 

 trunk, and each again is diverging into well-marked races, as rej)re- 

 sented by pcrloiKjo and neradensis. while many no doubt ai*e yet to be 

 discovered. 



Neradensis exhibits evidences of several incipient races. 



