144 Annals Entomological Society of America [Vol. V, 
Gonopods of female with claws very long and stout, moderately 
curved. First article excavated on mesal side toward base as usual, 
this side strongly chitinized as usual. Basal spines 2+2, large and 
stout, well separated, the outer larger than the inner on each side. 
Gradually and considerably attenuated cephalad, the first plate 
narrowest as usual. 
Length from 22 to 30 mm. A male 26 mm. long has antenne 11 
mm. long and anal legs as 9.5 mm. long with its tenth plate as 3.1 mm. 
wide. 
Locality: Mexico (Guadalajara and Tuxpan). 
Genus Guambius gen. nov. 
Type—lLaithobius euthus Chamberlin. 
Other known species belonging to this genus are pinguis Bollman, 
curtior Chamberlin and mississippiensis sp. n. described below. 
Guambius mississippiensis sp. nov. 
Dorsum dilute chestnut, with the caudal plates and a median longi- 
tudinal line somewhat darker. Head and antenne dark chestnut, the 
latter paler distad. Venter testaceous, darker brown caudad. Pros- 
ternum and prehensorial feet nearly the same as head. Legs testaceous, 
the caudal pairs a little darker. 
Head slightly wider than long (36: 35 or 34.5); widest at marginal 
interruptions, between which and the eyes the diameter is nearly 
uniform, the sides caudad of this convex and strongly converging; the 
median portion of caudal margin straight. Rather strongly trans- 
versely furrowed or depressed immediately in front of caudal marginal 
thickening, the furrow extending entirely across head and continuous 
with caudal ends of a wide longitudinal furrow extending cephalad 
dorsal of level of eyes on each side. A short transverse sulcus a little 
cephalad of and parallel with median part of frontal suture, a median 
longitudinal suclus extending forward from this transverse one and 
showing or passing through a deeper pit-like impression at middle of 
length. Smooth and shining, or only very obscurely uneven. 
Dorsal plates finely roughened. Major plates, excepting the 
seventh, showing distinctly the short transverse submarginal sulcus on 
each side about beginning of caudal third of plate, the seventh plate 
showing a similar sulcus near each caudal corner and one near each 
anterior corner as well. Most of the major plates marked with two 
distinct longitudinal sulci which diverge more or less from near the 
caudal margin cephalad, these sulci in some distinct only cephalad of 
the submarginal transverse marks. Posterior angles of eleventh and 
thirteenth plates a little produced, those of others rounded or obliquely 
excised. 
Most ventral plates with a rather deep longitudinal furrow toward 
each side but mesad of a weaker submarginal furrow also present. The 
usual median longitudinal furrow with also the transverse depression 
cephalad of caudal margin also more or less evident. 
