NEW NORTH AMERICAN CHILOPODS AND DIPLOPODS. 
By RatpH.V. CHAMBERLIN, 
University of Pennsylvania, Philadelphia. 
CLASS CHILOPODA. 
Family LITHOBIID. 
Genus Arenobius Chamberlin. 
Arenobius coloradanus sp. nov. 
Dorsum from testaceous to dark brown and dull chestnut with the 
posterior plates and the first one usually not all darkened. Head 
mostly the same color as dorsum or very nearly so, or somewhat more 
reddish. Antennz concolorous with head, pale distad. Venter from 
yellow or testaceous to dark brown, the caudal plates usually a little 
darker. Prosternum and prehensorial feet of same color as head or 
nearly so. Legs of same color as adjacent portion of venter. 
Head widest at level of marginal interruptions; clearly wider than 
long (11: 10); caudal margin straight. Depressed or furrowed parallel 
with frontal suture a little cephalad of the latter, from this furrow a 
median longitudinal furrow extending toward anterior margin. Two, 
usually clearly impressed, longitudinal furrows on caudal region of head, 
one a little each side of the middle and the two united in front of the 
posterior margin by a transverse furrow. Smooth and shining. 
Dorsal plates all very finely or obscurely roughened, appearing 
smooth and shining to the naked eye; usually no furrows distinctly 
developed excepting the usual depression or furrow immediately within 
the caudal and lateral margins and on some the short transverse mark on 
each side near margin at about one-third length of plate from caudal 
margin. Posterior angles of ninth, eleventh and thirteenth dorsal 
plates strongly produced; posterior angles of other minor plates rounded 
or obliquely excised. 
Ventral plates all punctate and finely roughened; impressed with 
three longitudinal furrows of which the median is most distinct, the 
latter on some of the more posterior plates ending caudad in a deeper 
pit or depression about one-third the length of plate from caudal edge; 
mostly with a rather wide transverse depression or furrow caudad of 
middle of plate. Sometimes an additional longitudinal furrow showing 
on each side between the median and the lateral, the caudal end often 
curving mesad to unite with its mate at middle; this furrow often more 
or less united with the lateral one. The last several plates sometimes 
with furrows very obscure or practically absent. 
Antenne short or very short, reaching the sixth or seventh segment; 
articles 30 to 35, the second very long with those more distad much 
shorter, cylindric, subuniform or, more usually, with longer articles 
occurring singly at intervals among the shorter ones, in general decreas- 
ing in size distad. Hairs of medium length. 
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