140 DIPLOPODA. 
1. Platyrachus bilineatus. 
Polydesmus bilineatus, Lucas, Hist. Nat. des Crust., Arachn. et Myriap. p. 523 (1840)*; Gervais, 
Ins. Apt. iv. p. 107°. 
Polydesmus (Stenonia) bilineatus, Saussure, Mém. Soc. Phys. Genéve, xv. p. 582, t. 7. fig. 50 (1860) *. 
? Platyrrhacus bilineatus, Attems, Denk. Akad. Wien, Ixviii. p. 847 (1900) *. 
Colour. Head, antenne, first tergal plate, and dorsal area generally dark olive-brown, with two narrow whitish 
stripes, somewhat widely separated from each other, extending from the 2nd to the 18th segments ; 
anterior and lateral edges of the keels, the tubercles along the posterior border of the segments and on 
the lateral margins of the keels also whitish ; underside brown or yellow-brown. 
Apart from colour, this species seems to resemble for the most part those grouped round P. limonensis. The 
keels are large, standing somewhat high on the sides, and horizontal; their anterior edges are convex, 
their posterior edges concave, both being serrulated; lateral margin with about five tuberculiform teeth ; 
the posterior angle produced and acute in the hinder half of the body, but not spiniform. Pores remote 
from the edge. Dorsal area granular; a row of tubercles along the posterior edge and two less distinct 
rows in front. Caudal process rounded. 
Length of $ (typical example) 63 millim., width 11. 
Hab. Mextco !-3, 
Saussure’s description of this species was taken from the typical example in the 
Paris Museum. It is said to have come from Mexico. The example described by 
Attems ‘ as P. bilineatus came from Oliverea, in Peru, and probably represents a different 
species. It measures 80 millim. long and 18 broad. 
2. Platyrachus mexicanus. 
Polydesmus mexicanus, Lucas, Hist. Nat. des Crust., Arachn. et Myriap. p. 523 (1840)*; Dict. Sci. 
Nat. d’Orbigny, Myriap. t. 1. fig. 3°; Gervais, Ins. Apt. iv. p. 107°. 
Polydesmus (Stenonia) mexicanus, Saussure, Mém. Soc. Phys. Genéve, xv. p. 534, t. 7. fig. 51 (1860) *. 
?? Platyrrhacus mexicanus, Attems, Denk. Akad. Wien, Ixviii. p. 848 (1900) ’. 
Colour obscure, with two pale longitudinal lines as in P. bilineatus, but believed by Saussure to be attributable 
to discoloration. 
Large ; keels horizontal, lamellar, very wide, shaped as in P. bilineatus, but narrowing a little externally in 
the median portion of the body; their anterior border less regularly arched, being more strongly arched 
proximally than distally and not denticulated ; the posterior border less regularly concave ; the external 
border not finely toothed as in P. bilineatus, but armed with four or five long spiniform teeth, of which 
the last is divided posteriorly and is a little incurved on segments 15 and 16 to form a kind of hook ; 
keels of 17th less regularly toothed and more or less truncated posteriorly. Pores very large and 
far removed from the lateral edge of the keels. Dorsal surface obscurely granular; a row of tubercles 
traceable along their posterior border. 
Length (minus head and segments 1 to 5) 75 millim., width 17. The total length was probably over 
90 millim. 
Hab. Mexico !~, 
This species appears to be very incompletely known. ‘The examples that Attems 
identified and described under the name P. mewxicanus differ in several respects from 
the type as described by Saussure, in size, colour, height of the keels, shape of 
their anterior border, distance of the pore from the lateral margin, tuberculation of 
