COLOBOGNATHA. 4] 
Class DIPLOPODA, Blainville. 
Subclass CHILOGNATHA. 
The known Central-American Diplopoda are referable to the following sections. On 
account of the diversity of opinion as to the value to be assigned to these sections, it is 
proposed in the following pages to designate them merely as “ groups,” setting aside the 
question as to whether they should take ordinal, subordinal, or superfamily rank :— 
a. Mandibles degenerate or wholly suppressed ; labral area of head pointed ; 
eight pairs of legs in front of the legs of the seventh segment . . . . CoLoBOGNATHA. 
6. Mandibles not degenerate; labral region broadly truncated and emar- 
ginate ; seven pairs of legs in front of the legs of the seventh segment. 
a’, Tergal plates furnished with three symmetrically disposed pairs of 
setze ; without scent-pores ; sterna not coalesced with terga. . . . CHORDEUMOIDEA. 
b'. Tergal plates without such setz ; more or fewer with scent-pores; sterna, 
except on a few of the anterior segments, invariably coalesced with 
the terga (at least in the known Central-American species). 
a’. Number of segments great and inconstant in the species; from 
the fifth or sixth to the penultimate with a pair of scent-pores ; 
phallopods of ¢ internal and derived from the posterior appendages 
ot the seventh segment. 
*, Stipites (lateral plates) of enathochilarium mesially in contact 
proximally . . . . oS an . + « « . + Junorpea. 
Bb. es of gnathochilarium widely separated proximally. 
*, Segments 1-5 with a single pair oflegs . . . . . « « . SPIROBOLOIDEA. 
* Segment 4 apodous, segment 5 with two pairs of legs. . . . SprrosTREProrpEa. 
6°, Number of segments constant, 19 or 20; many without scent- 
glands; phallopods external, derived from anterior legs of seventh 
segment . 2 1. 2 6 eee eee ee ee ee ee 6+) 6 POLYDESMOIDEA. 
Group I. COLOBOGNATHA. 
Number of segments large and very variable within the species, with eight pairs of appendages in front of 
those of the seventh segment. None of the anterior segments apodous, the first four bearing one pair 
of appendages each, the fifth, sixth, seventh, and following segments, except the last two, which are 
limbless, with two pairs*. Head with its labral region narrowed or pointed distally; mandibles 
degenerate or suppressed; gnathochilarium narrowed distally, the mouth-parts being suctorial or 
* JT here adopt; at all events for the time being, the usual interpretation of the disposition of the 
appendages with reference to the segments, in preference to that put forward by Cook, who assigns a single 
pair ‘of appendages to the first five segments, and two to each of the following segments, regarding the 
gonopods of the male as derived from the posterior pair of the seventh and the anterior pair of the eighth, 
BIOL. CENTR.-AMER., Diplop., November 1903. G 
