176 THE CANADIAN ENTOMOLOGIST. 



The genus, which is compact, can readily be detected by the charac- 

 ter of the prosternai teeth. 



Genus Taiyub'ms gen. nov. 



This genus is very close to the preceding, but the species composing 

 it may always be at once distinguished by the characters of the prosternum, 

 the teeth of which are the same in number but differ in not having the 

 inner teeth borne far forward, and in having the axis of each of the latter 

 directed somewhat mesad of directly cephalad, with the line tangent to 

 apices of teeth curving caudad from the sides mesad, i.e., this line clearly 

 recurved. Antenne^ short, or very short, consisting of from 26 to 3g 

 articles. Posterior coxse either entirely unarmed laterally or with each 

 one of last pair or of last two pairs with a weakly developed spine which 

 is often difficult to detect. Anal legs always with two claws ; penult with 

 two or three. Dorsal spines of anal legs, 1,0,3,1,0; of penult, 1,0,3,1,1. 

 Anal and penult legs very nearly as in Paitobius. Gonopods nearly as in 

 Faitobius, but basal spines characteristically much broader and wider near 

 middle of length. Pigmentation much as in preceding genus. In known 

 species posterior angles of gth, nth, and 13th dorsal plates produced. 



Type. — T. angelus Chamberlin. 



Distribution. — Western United States. 



Other species belonging to this genus in addition to the type are 

 satanus Chamberlin, harrielœ Chamberlin, and ///r////'^//^ Chamberlin. 



Genus Sonibius gen, nov. 



Related to the two preceding genera which it replaces in the north 

 central section of the country. The prosternai teeth small and subequal, 

 2 4- 2 or 3 + 3 in number, with the line of their spaces recurved. 



Readily distinguished from the preceding two genera in having the 

 short antennae composed normally of but twenty articles which are 

 relatively long, whereas in Paitobius and Taiyubius they are mostly very 

 short and crowded. Last two or three pairs of coxae laterally armed, 

 last four or five pairs dorsally armed. Anal legs armed with two or three 

 claws as are also the penult, the number being mostly three. Dorsal 

 spines of anal legs 1,0,3,1,0; of penult and 13th always 1,0,3,1,1. Gono- 

 pods of female with claw partite. Basal spines characteristically short and 

 broad. Adults not showing the peculiar reddish-purple pigment in deeper 

 tissues manifest in Paitobius and Taiyubius. Dorsum always smooth and 

 shining. In known species posterior angles of 9th, nth, and Î3th dorsal 

 plates produced. 



