1912] Chilopods and Diplopods 143 
Body rather slender being about 7.5 times as long as width of tenth 
plate; conspicuously attenuated cephalad from eighth plate, with the 
first plate much narrower than the third. Width of head, first, third, 
eight and tenth dorsal plates to each other as 40, 33, 37, 47 and 47, the 
eight and tenth plates being equal and manifestly considerably wider 
than the head. 
Length from 12 to15mm. A male 13 mm. has antenne 5 mm. long 
and anal legs exclusive of coxa, circa 4.8 or 5 mm. long, with the tenth 
plate about 1.7 mm. wide. 
Locality: Manitou, Colorado (author, Aug., 1910). 
Arenobius sontus sp. nov. 
Brown to deep mahogany. Head in some degree darker than 
dorsum. Antenne chestnut, paler distad. Prosternum brown to 
mahogany, paler than head. Venter testaceous to deep brown, the 
caudal plates darkest. Legs testaceous to brown, the posterior pairs 
darker with their tarsi usually paler. 
Head and first dorsal plate smooth and shining; other dorsal plates 
rugose, the more caudal ones more strongly roughened than the anterior 
ones. 
Antenne of moderate length, reaching the seventh segment. Com- 
posed of from 40 to 50 articles which beyond the first ones become 
short, often showing an alternation of a very short article with longer 
“ones in groups between. 
Eyes composed of mostly 9 to 12 ocelli arranged in three series; 
thus, 1-+3, 4, 2. 
Prosternal teeth 2+2, the two fused at base in a dental plate, the 
inner larger than the outer and both much stouter than the ectal spines 
which, nevertheless, is stout and tooth-like and not at all bristle- 
tipped. 
Coxal pores circular decreasing markedly in size proximad, the 
most distal being large; in number and arrangement, 5, 5, 5, 4; 5, 5, 5, 5,; 
6:76, 6;.5,etc: None of the posterior coxee armed laterally. Spines 
of first legs, ; 3 ' z : or 4 a: ; ; of second eet of third to 
sixth, aa a of seventh and eighth, SEE of ninth and tenth, 
Nog 5: ; : = of eleventh, ee 3 ; ; 2 of twelfth, ea : : 5 s of penult, 
ee ra s~O anal, nea 5 - with two claws, the penult hav- 
ing three. As noted in the formule, the dorsal spine of the posterior 
coxe is frequently replaced by two situated close together. The anal 
legs of the male slender, the tarsal joints especially slender; tibia bear- 
ing near distal end of its mesal surface toward dorsal side a small, 
flattened, subtriangular lobe or crest the long axis of which is parallel to 
that of the joint and its higher end caudad, its mesal or long edge 
somewhat convexly curving. Penult legs slender bearing no special lobes 
Gonopods of male rather large and broad, conspicuously exposed; 
distally rounded, bearing about ten or twelve long bristles. 
