chamberlin: chilopods from Mexico and west indies. 533 



Prosternal teeth 3 + 3 (or 3 + 4). A sinus present, wide, and 

 semicircularly rounded at bottom. Spines ectal in position, small and 

 bristle like. 



Posterior angles of ninth, eleventh, and thirteenth dorsal plates 

 produced. Fourteenth plate normal. 



Coxal pores circular; uniseriate. 



Claw of female gonopods long and entire. Spines 2 + 2, stout, 

 subconical. 



Anal legs in male not specially modified but penult with fifth joint 

 bearing at distal end on mesal or caudal surface a longitudinally 

 placed swelling or crest suggesting that of species of Guanibius but 

 proportionately larger and different in position. 



Posterior coxae either wholly unarmed, or the last two or three 

 armed dorsally while the anal pair may also be armed laterally. 

 Dorsal spines of anal legs 1 (0), 0, 3, 2, 0; ventral, in genotype, 0, 1, 2, 

 2, 2; claws 2. Dorsal spines of penult legs 1, 0, 3, 2, or 5, 0, 3, 2, 0. 

 Ventral spines of first legs 0, 0, 0, 0, 1; dorsal 0, 0, 2, 1, 1. First nine 

 to thirteen pairs of legs with but a single dorsal tibial spine. 



Length averaging near 20 mm. 



Genotype. — D. simplex, sp. nov. 



In lacking a median ventral spine on the third and fourth segments 

 of all legs, this genus is unlike any other lithobioid known to the writer. 



Delobius simplex, sp. nov. 



Dorsum chestnut or with some of middle plates deep brown, with 

 no distinct chestnut tinge; with irregular dusky streaks. Head like 

 dorsum or color slightly clearer. Antennae dark brown proximally, 

 paler and somewhat rufous distad. Prosternura and prehensors 

 dilute chestnut, the latter of pale ferruginous cast distad. Venter 

 light brown, the caudal plates darker. Legs brown; the posterior 

 pairs darker, the tarsi, excepting proximal portion of first article, 

 dilute ferruginous. 



Body in male type 8.5+ times longer than width of tenth plate 

 Width of head and of first, third, eighth, tenth, and twelfth plates 

 to each other as 53 : 47 : 49 : 56 : 55 : 52. 



Head wider than long in about ratio 53 : 50. Head wider just back 

 of eyes than at breaks. Caudal margin mesally weakly incurved. 

 A longitudinal median sulcus which is deepest in front of frontal suture 

 but which crosses the latter and is traceable to a transverse furrow 

 some httle distance in front of the caudal marginal thickening. 



Antennae short, not very slender distad. Composed of 36-38 



