Occasional Papers of the Mnsenin of Zoology 21 



a. Eyes twice or more their greatest diameter apart. 



b. Repugnatorial pores contiguous with segmental sutures. 



S. atoporus. 

 bb. Repugnatorial pores well removed from sutures. 



c. Last tergite transversely sulcate; segments sixty-five. 



A'', astix. 



cc. Last tergite not transversely sulcate; segments fifty-five 

 to fifty-six. 



d. Collum angled below, with four striae; anal scale with 

 caudal margin only weakly convex, not mesally angled. 



A', orthacanthus. 

 (Id. Collum with lower margin straight, only two striae; 

 anal scale with caudal margin strongly angled. 



A'', gracilior. 



aa. Eyes clearly less than twice their greatest diameter apart. 



b. Segments of middle and posterior region of body striate up to 



or nearly to pore; suture strongly ribbed throughout; eves 



about 1.4 times their diameter apart. U. eustiiatus. 



bb. Segments of middle and posterior region of body striate only 



beneath; eyes less than their diameter apart. 



c. Posterior angle of last tergite and of anal scale obtusely 



rounded. O. (laigci. 



cc. Posterior angle of last tergite and of anal scale acute. 



d. Last tergite with caudal portion set off or crossed l)y 

 one or two sharply impressed transverse sulci; seg- 

 - ments fifty-eight to sixty-one. Anterior angle of col- 

 lum of female produced. 

 e. Second stria curving upwards in front as usual ; 

 next to uppermost stria very short, crossing only 

 caudal border. 0. icalkcri. 



ee. Second stria short, straight, not curving upwards 

 anteriorly ; next to uppermost stria complete, not 

 there abbreviated. O. foliatiis. 



dd. Last tergite at most with a very shallow transverse 

 depression, no sharply impressed sulcus, segments 

 fifty-four to fifty-five. .Anterior angle of collum of 

 female subrectangular, male conspicuously produced. 



O. ctliola.r. 



