532 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
of penult legs 0, 0, 3, 2, 2. The anal leg in the male bears a lobe at 
distal end of tibia on mesal side. 
GENOTYPE.— A. mirabilis, sp. nov. 
This genus is remarkable because of the greatly enlarged tergite of 
the fourteenth segment, a feature at once separating it from all others. 
ATETHOBIUS MIRABILIS, sp. nov. 
Dorsum chestnut. Head back of the suture and the first dorsal 
plate a little darkest. Antennae typically darker distad than proxi- 
mad. 
Antennae reaching to middle of the fifth segment; articles above 40, 
in type being 43. 
Eyes composed of about 13 ocelli in four series: e. g., 1 + 3, 4, 4, 2. 
Single ocellus large, subcircular, pale. Most caudal ocellus of top 
series much larger than the others but smaller than the single one, 
often pale. Other ocelli black. 
Prosternal teeth acute; well separated; the inner one on each side 
a little larger than the outer; line of apices distinctly recurved. 
Spines stout, more or less dentiform. 
Posterior angles of seventh, ninth, eleventh, and thirteenth plates 
strongly produced; processes broad and long, distally more or less 
rounded. Fourteenth plate greatly enlarged, subcircular, covering 
the fifteenth. 
Coxal pores large, circular, mostly 3, 4, 4, 3. 
Claw of female gonopods entire as usual. 
Spines of penult legs, net of the anal ie 3 - . with two claws. 
None of coxae armed. 
Anal legs in male slender and short. The tibial process small, 
subcylindric, the article at its level being about 3.66 times as wide as 
the process is thick. 
Length up to 24 mm., that of the type being 22.5 mm. 
Locatity.— Mexico: Distrito Federal; Esclava (O. W. Barrett). 
‘TLypn, MC. 2.1758. 
DELOBIUS, gen. nov. 
Head with lateral marginal breaks small but distinct. 
Antennae short or intermediate; composed of thirty-six or more 
articles. 
Eyes composed of seriate ocelli; the ocelli few. 
