198 DIPLOPODA. 
4. Rhysodesmus stolli, sp.n. (Tab. XV. figg. 3, 3.) 
3. Colour (? decolorised) olive-grey with the keels and caudal process yellower than the metazonites; the 
metazonites above brownish, especially in their posterior half; prozonites pale; first tergal plate with 
median brown central patch; antenne yellow ; legs yellow, with two basal segments darker and rather 
sharply contrasted in tint with the sternal areas, which are whitish grey. Body robust, attenuated 
anteriorly from the 5th segment and posteriorly from the 17th, with the keels normally overlapping and 
depressed, but well developed. Antenne short, width of head equal to length of segments 2 to 5 inclusive ; 
segments 2 to 6 subequal in length. First tergal plate with anterior border only very lightly convex 
mesially, obliquely cut away laterally, lateral angle bluntly acute, posterior border lightly sinuous. 
Dorsal surface of body nearly smooth, only finely coriaceous in the middle; but becoming much more 
coarsely so on the lateral slope and on the upper side of the keels, which do not quite follow the slope of 
the metazonites, with two to three rows of obsolete granules and coriaceous in the shallow depression 
just behind the anterior ridge, which is laterally continuous with the ridge or crest of the anterior 
border of the keels. Keels with anterior border convex, and rounded anterior angle; the lateral marginal 
thickening well developed ; posterior border very lightly concave, slightly prominent at shoulder and notched 
at the base; with the posterior angle a little produced, but becoming gradually more so in the hinder 
half of the body ; the posterior border inclined obliquely backwards from about the 15th; keels of 19th 
small, apically rounded, only surpassing by a little those of the 18th. Pores in the anterior half of the 
keel, except at the posterior end of the body, but never near the apex. Caudal process triangular with 
truncate apex; anal sternal plate semicircular, with setiferous tubercles wide apart. Sternal areas 
considerably wider in front than behind; mesially depressed, with mesially abbreviated transverse 
sulcus, which is deep only between the two legs on each side, its posterior border produced a little on 
each side beyond the coxal cavity, lightly emarginate but becoming more pronouncedly so and in some 
cases bitubercular in the posterior half of the body, especially on the 17th segment. The ridge between 
the two zonites curving backwards in front of the base of the keel to meet at an acute angle, the dorsal 
ridge passing inwards from the anterior edge of the keel. Legs short, with spine of second segment 
well developed, about as long as the claw ; terminal segment short, shorter than the third and not much 
longer than the fourth segment. Phallopods shortish, nearly in contact, crossing at the tip of the 
seminal stile, which is pointed when viewed from below, triangularly expanded from the side and lightly 
upeurled ; auxiliary branch directed obliquely forwards and upwards, turned forwards at the tip and 
rising from about the middle of the upper side of the organ. 
Length (¢, @ undistended) about 47 millim., width 12; length of antenne 7 millim. 
Hab. N.W. Guatemaua, Retalhuleu (StolZ). 
5. Rhysodesmus tabascensis, sp. n. (Tab. XV. figg. 2, 2a.) 
2. Closely allied to the preceding species in colour and structural characters, but with the anterior border 
of the keels more obliquely cut away externally, so that the anterior angle is more obtuse and less rounded 
and the posterior borders of the sternal areas are much more strongly bidentate. 
Length about 42 millim., width 11. 
Hab. Mexico, Teapa in Tabasco (H. H. Smith). 
6. Rhysodesmus championi, sp. n. 
2. Colour as in R. stolli. Antenne short, width of head about equal to segments 2 to 6 inclusive. 
Allied to the two preceding species (R. stolli and R. tabascensis), but thinner, the anterior ridge of 
the keels less convexly produced, though the nature of the curvature more resembles that of R. stolli 
than that of R. tabascensis; the posterior angles from the 5th segment backwards produced, more 
so than in either of these forms; the keels of the 19th far surpassing those of the 18th, and the 
anal sternal plate markedly more triangular, its sides being nearly straight and the area between 
