RHYSODESMUS. 209 
Hab. Guatemata (Rodriquez 1). 
This species differs from ail those known to me in the structure of the phallopods. 
In some particulars it seems to resemble R. stolli, but certainly differs from it in the 
shape of the auxiliary branch of the phallopod. | 
Brolemann (lec. cit. p. 102) also records, but does not name, a second species from 
Guatemala, which somewhat approaches apparently R. zendalus, Sauss., in colour, but 
has the keels entirely pale. The ? measures 48 mm. long and 10 wide. 
27. Rhysodesmus vicinus. 
Polydesmus (Fontaria) vicinus, Sauss. Linn. Ent. xiii. p. 8322 (1859)'; Mém. Soc. Phys. Genéve, 
xv. p. 318 (1860) ’*. 
3. Colour ?white. Very nearly allied to R. otomitus, but much smaller, more vermiform, with the 
posterior angle of the keels a little elevated triangularly ; a shallow groove running obliquely from the 
anterior angle of the keel to its posterior border; posterior angle of the 19th rounded. 
2 with the body more vermiform and the keels smaller. 
Length 17 millim., width 4, 
Hab. Mexico, cold regions, the plateau of Anahuac, also Oaxaca in the tropical 
regions ! ?, 
28. Rhysodesmus zapotecus. 
Polydesmus (Fontaria) zapotecus, Sauss. Mém. Soc. Phys. Genéve, xv. p. 314, t. 2. fig. 11 (1860)’; 
Humb. & Sauss. Miss. Sci. Mex., Myr. p. 37 (1872) °. 
Colour uniformly brown. Dorsal surface very little convex, but the keels following its slope, wide, their 
anterior borders prominent, the posterior concave, excised, with a small basal prominence; anterior 
angle rounded, posterior with a tolerably sharp tooth beginning on the 7th, 8th, or 9th segments ; marginal 
thickening even, pores superior, in the middle of the thickening on the Sth and 7th and thereafter 
becoming more and more posteriorly placed. 
-¢. More flattened, the dentiform lobes of the posterior angles more pronounced. 
Length, 2, 29 millim., width 5. 
Hab. Mexico, San Andres Tuxtla &c.!?. 
This species is said to be characterized by the length of the spines on the legs, the 
slenderness of the body, the dentiform process of the posterior angle of the keels, and 
the emargination of the posterior border of the keels. 
29. Rhysodesmus zendalus. 
Polydesmus (Fontaria) zendalus, Humb. & Sauss. Rev. et Mag. Zool. (2) xxi. p. 150 (1869) °; 
Miss. Sci. Mex., Myr. p. 34, t. 2. figg. 1, 1 @ (1872) *. 
2. Colour. Body testaceous, but the dorsal surface barred transversely with olive-black across the posterior 
half of the metazonites and on the keels; head pale, darker on the front; entenne and legs 
brown. 
Compared with 2. fraternus, acolhuus, and mystvcus: back arched, keels moderate, not markedly wide, 
a little elevated, and squared; the posterior border of keels 2 to 5 shghtly oblique forwards ; that of 
BIOL. CENTR.-AMER., Diplop., April 1910. 25 
