208 DIPLOPODA. 
yellow, the yellow patch on each keel nearly as wide as the median brown area ; first tergal plate with 
only a median patch; prozonites apparently pale like the lateral and inferior portions of the segments ; 
head pale; antenne pale, with apical segment infuscate; legs pale. Body stout, compact; dorsal 
surface vaulted, the keels following the slope of the median area; their anterior angles rectangularly 
rounded ; the posterior angles not spiniform or directed posteriorly ; posterior border directed a little 
forwards on the 4th to the 8th segments, slightly convex from the 8th to the 14th, lightly inclined 
backwards on the 15th and 16th, and strongly oblique on the two following; keels of the 18th 
triangular posteriorly. Pores opening in the middle of the lateral border. Dorsal surface vaguely 
striolate and coriaceous, the keels with two often indistinct rows of granules. 
3. With all the keels more elevated as in other species, those of the 15th to the 17th directed more obliquely 
posteriorly. 
Length, 2 (contracted), 43 millim., width 10. 
” 3 (distended), 55 ,, ” 9. 
Hab. Mexico, mid-region of the Eastern Cordillera (Cordova [| ¢, type], Moyoapan, 
Santa Cruz, near Orizaba [ @ ]). 
25. Rhysodesmus toltecus. 
Polydesmus (Fontaria) toltecus, Sauss. Linn. Ent. xiii. p. 322 (1859) (2) '; Mém. Soc. Phys. 
Genéve, xv. p. 325, t. 4. figg. 22, 23 (1860) °*. 
Polydesmus (Fontaria) mayus, Sauss. Linn. Ent. xiii. p. 822 (1859) (¢)’. 
Polydesmus (Leptodesmus) granulosus, Sauss. Linn. Ent. xiii. p. 823 (1859) (¢) * 
Colour brown, with the end of the keels pale; altogether porcelain-white when dry. Formas in 2. totanacus, 
but with the body more vaulted ; keels not quite continuing the slope of the back, shaped almost as in 
R. totanacus, but the lateral borders a little thicker and the posterior angle showing a tendency to form 
a small projection. All the segments except those quite at the anterior and posterior ends of the body 
marked with three irregular transverse rows of rounded polished tubercles. 
$. Much flatter than the female; the keels horizontal, uptilted externally, so that they appear to be 
separated by a gutter from the median convex area of the segments. 
Length, 2, 36 millim., width about 8. 
2” 3 ’ 33 ” ” ” 7. 
Hab. Mexico, the eastern slope of the Cordillera and the edge of the plateau 
(Cordova, ? Peak of Orizaba, 3000 metres) 1~*. 
Distinguishable from all the species known to me by the distinctness of the three 
rows of tubercles on the dorsal area of the segments. 
26. Rhysodesmus violaceus. (Tab. XV. fig. 15.) 
Fontaria violacea, Brélemann, Mém. Soc. Zool. France, xiii. p. 101, t. 6. figg. 33-36 (1900) *. 
Colour violet-brown, with whitish keels, the pale colour sometimes extending along the posterior border of 
the median area of some of the segments. Body robust, a little attenuated anteriorly. Dorsal surface 
nearly smooth, becoming coriaceous upon the keels. first tergal plate with anterior and posterior 
borders nearly straight in the middle, abruptly cut away laterally ; the lateral angle acute, with blunt 
point; posterior angles of the keels almost rectangular, entirely so in segments 5 to 14; behind the 
15th becoming more acute. Sterna unarmed. Phallopod with principal branch lightly curved upwards 
(? inwards), stout and short, considerably shorter than the palmar portion; auxiliary branch stout, 
rather long, straightish, somewhat abruptly hooked at the apex. 
Length, 9, about 45 millim., width 10, 
» oy ” ” » oe. 
