RHYSODESMUS. 195 
is more in evidence the prozonites are posteriorly brown and almost as 
dark as the metazonites. 
d. Metazonites pale, with a narrow dark transverse anterior streak 
expanding laterally into a conspicuous dark spot close to the anterior 
base of the keel; prozonites pale; first tergal plate with dark patch 
almest divided; head and antenne dark . . . . . totanacus. 
d'. When the pattern approaches that of R. totanacus the prozonites at 
least are brown. 
e. Prozonites pale and sharply contrasted with the dark hue of the 
metazonites . . . . . . attemsi, tabascensis, ? lima, ? stolli, ? championi. 
. Prozonites dark and gradually shading into the dark hue of the 
metazonites. 
f. Distinctly transversely banded, the posterior portion of the meta- 
zonites yellow from keel to keel, the dark patch on the first 
tergal plate bounded behind by yellow; anterior area of meta- 
zonites with a thickish transverse brown stripe expanding close 
to the base of the keel into a larger patch. . . . inustus, flavocinctus, nahuus. 
f'. Not distinctly banded transversely, the metazonites either 
uniformly brown or a little paler behind, sometimes with a pale 
median patch, which, however, does not reach the yellow of the 
keels; dark patch on first tergal plate continued to its posterior 
border or only indistinctly and partially separated therefrom . . salvini, godmani, 
arcuatus, notostictus, ? toltecus, ? montezume, ? fraternus, ? violaceus, ? angelus. 
1. Rhysodesmus montezume. (Tab. XIV. figg. 6, 6a; XV. fig. 8.) 
Polydesmus (Fontaria) montezume, Sauss. Linn. Ent. xiii. p. 821 (1859)'; Mém. Soc. Phys. Genéve, 
xv. p. 308, t. 2. fig. 9 (1860) *. 
Nec Fontaria montezume, Attems, Denk. Akad. Wien, lxviii. p. 258 (1900) *. 
Colour (in alcohol) a tolerably uniform pale olive-green, with the antenne and the distal segments of the legs 
ochre-yellow. 
Body slender and Leptodesmus-like, with keels small, not overlapping. 
Head with frontal sulcus ; antenna short; width of head equal to length of segments 1 to 5. First tergal 
plate with anterior border evenly convex; lateral angle rounded; posterior border laterally inclined 
forwards ; keels of 2nd and 3rd with posterior border also directed obliquely forwards, with the 
posterior angle obtuse, and the anterior angle widely rounded. Dorsal area nearly smooth, only finely 
sculptured; the sulcus lineolate; three indistinct rows of granules. eels small, markedly wider 
posteriorly than anteriorly ; the anterior border very short, passing abruptly into the lateral border, the 
angle being very obtuse and rounded; the lateral margin considerably thickened ; the posterior border 
produced, convex, separated by a distinct notch from the posterior border of the median portion ; posterior 
angle rounded, never spiniform, surpassing the posterior bordor of the median portion only on segments 
16 to 19. The keels even in the male rising low on the sides, but in this sex not following the slope of 
the back. Pores on the posterior half of the lateral surface, near its middle on the 5th keel, which has 
its posterior border inclined forwards slightly. Caudal process triangular, truncated; anal sternal 
plate subtriangular, an anguliform process between the setiferous tubercles. Sternal areas laterally 
notched; posterior border lightly emarginate ; indistinctly longitudinally sulcate. Legs only moderately 
long, thickish, spine strong, terminal segment about twice as long as the penultimate. Phallopods 
when viewed from below with distinct sinuous curve distally, the points projecting straight forwards, not 
2c2 
