526 Mr. R. 1. Pocock on the Morphology and 
segment, and therefore themselves to belong to the third 
segment. But in the females of three Central-American 
species dissected by myself these appendages arise from a 
small sternal plate separated by a very distinct membranous 
area from the genital plates. Finally, in the immature or 
Pseudoiulus stage of Paraiulus aztecus the arrangement of 
the appendages is the same asin Julus—that is to say, the first 
appendages lie between the gnathochilarium and the inward 
prolongations of the second segment, the second appendages 
behind the latter and the corresponding area of the third 
segment, and the third appendages are attached to the sternal 
plate which is fused to the tergum of the fourth segment. 
Thus Julus and Paraiulus are in agreement in these respects. 
Although resembling Paraiulus in many striking parti- 
culars, Mongoliulus differs from that genus in both sexes in 
certain structural characters which have, in my opinion, 
a greater taxonomic value than those which serve to 
distinguish the three so-called families, Iulide, Blaniulide, 
and Nemasomide (Isobatide). If these three groups and 
the Peromopide retain the rank assigned to them by Cook 
and Silvestri, consistency will compel the adoption of a 
section of the same rank, the Mongoliulide, for Mongol- 
iulus. Even if they be reunited under the one heading 
Julide, a strong case could still be made out for the recog- 
nition of the Mongoliulide, especially since further researches 
into the structure of the various species now included under 
the names Paraiulus and Ptyoiulus will no doubt bring to 
light materials for the splitting of these genera into several 
additional genera, equivalent to those into which the old genus 
Julus has been broken up by Berlese and Verhoeft. 
The differential characters of the Mongoliulide, Para- 
julidee, and Peromopide, as compared with the better-known 
Tulide and related European families, may be tabulated as 
follows :— 
a. Mandibles with about ten rows of pectinations. 
a’. Male with first ley enormously developed, 
forming a five- or six-joimted clasper ; 
second legs dwarfed (? sometimes sup- 
pressed) and attached to a sterno-coxal 
plate showing scarcely a trace of sutures; 
enathochilarium with promentum oval, 
armed with a downwardly directed tooth- 
like process, the lingual lobes crescentically 
curved on each side of it; each of the 
coleopods, consisting of two independently 
movable processes, subequal in length. 
a*, Male with legs of first pair six-jointed, 
of second pair, when present, small, 
