524 bulletin: museum of compaeative zoology. 



Antennae short and thick, near 2.5 times longer than the head. 

 Ultimate article distally obliquely truncate; shorter than the two 

 preceding articles taken together. 



Claws of prehensors when closed extending much beyond anterior 

 margin of head, attaining distal end of second antennal article. Claw 

 at base with a stout conical black tooth just distad of which is a pale 

 protuberance. Femuroid at distal end with a much thicker, paler, 

 distally rounded process or tooth extending in a distomesal direction; 

 near middle of length showing also a slight rounded protuberance. 



Prosternum with anterior margin bearing two acute teeth close 

 together, the sinus between them being narrow and not deep, its 

 bottom straight. Sides subparallel from anterior end to rounded 

 caudal corners. Wider than long in about ratio 7:6; 1.54 times longer 

 than ectal height of femuroid. 



Dorsal plates deeply bisulcate; a pair of weaker intermediate sulci 

 more or less developed on some of the plates or in place of these a 

 single median sulcus on most anterior plates. A transverse sulcus, 

 angulate at middle, evident on some of anterior plates. 



Anterior prescuta very short; the others increasing in length caudad 

 and becoming long in the middle and posterior regions. 



Spiracles all circular; the anterior one much larger than the third 

 with the second intermediate; others of moderate size and not much 

 varying from anterior to posterior regions. 



Ventral plates wnth a distinctly impressed median longitudinal 

 furrow which is deepest at middle of length, in some plates with a 

 vague transverse furrow crossing this at middle. 



Ventral pores free; present on anterior plates in a narrow transverse 

 band across caudal border. Last ventral plate with sides conspicu- 

 ously converging caudad; straight or a little incurved. Width across 

 anterior end to width across caudal as 9:5; length to greatest width 

 as 10:9, twice the width at caudal end. 



For dorsal plate see Plate 5, fig. 6. 



Coxopleurae of anal legs moderately enlarged. Pores small and 

 numerous both below and above but not present on most caudal 

 portion ventrally and on a still larger caudal area dorsally. 



Anal legs much longer than the penult. Slender; the last article 

 slender and moderately narrowing distad. Hairs moderately long, 

 sparse. Clawless. 



Pairs of legs in most cases 45; rarely 43 or 47. 



Length 23 to 35 mm. 



Locality. — Mexico: Hidalgo, Guerrero Mills (W. M. Mann). 

 Type, M. C. Z. 1730; manv specimens, Tvpe and Paratvpes, M. C. Z. 

 1750. 



