180 DIPLOPODA. 
nearly horizontal keels. Acels of segments horizontal, with rounded anterior angle and with posterior 
angle backwards to the 14th or 15th segment rounded, behind that point angular and lightly produced 
posteriorly. Pores normal in number, the area round them more or less distinctly thickened. Dorsal 
area flattish or vaulted, without transverse groove. Caudal process of anal segment conical ; anal sternal 
plate triangular, with two small bristle-bearing tubercles. Sternal areas wider than long. Phallopods 
without coxal calcar ; second segment long and strong, branched distally, bearing on the inner side a 
wide distally open seminal fossa. 
Type, WV. swmichrastt, Humb. & Sauss. 
Distribution. Central America. 
This genus, known to me only from figures and description, is nearly allied to 
Acutangulus, and the two may be found to intergrade through such forms as 
N. vermiformis and NV. orizabe, in which the structure of the phallopods is unknown. 
The four species here referred to Neoleptodesmus seem to be separable by the 
following features :— 
a. Body attenuated in front, the 1st segment being narrower than the 8rd... . vermiformis. 
a‘. Body as wide in front as in the middle, the 1st segment as wide as the succeeding 
ones. 
b. Pores not borne upon definite button-shaped or tuberculiform excrescences. 
C. - Kecls very small and linear, with posterior angles rectangular . . . . orizabe. 
. Keels comparatively large, with the anterior and posterior angles widely | 
rounded; (phallopod nearly straight, its median branch bué little expanded 
apically) 2 6 we ee ee ee we SuMIChrasti. 
b'. Pores borne upon distinct tuberculiform excrescences; (phallopod arcuate, 
its median branch much expanded at the distalend). . . . . . . 0.) aztecus. 
1. Neoleptodesmus aztecus. 
Polydesmus (Leptodesmus) aztecus, Sauss. Linn. Ent, xi. p. 324 (1859)'; Mém. Soc. Phys. 
Genéve, xv. p. 801, t. 1. fig. 5 (1860) ’. 
Polydesmus (Oxyurus) aztecus, Sauss. & Humb. Miss. Sci. Mex., Myr. p. 160 (1872) °. 
Colour whitish. Segments smooth and shining. Body cylindrical, slender, and elongate, the keels of the 
mid-region of the body widely separated on each side. rst tergul plate as wide as those of the rest of 
the body, with rounded angles and finely bordered. eels of segments 2 to 4 sloping and directed 
slightly forwards; the following keels very short, almost as in Strongylosoma, rounded, bordered, and 
ending laterally in small prominences bearing the pores ; on the 19th segment the keels are represented 
by small backwardly-directed tooth-like processes. Caudal process of anal segment slightly down-bent 
apically ; sternal plate triangular. 
3. Keels larger, higher on the sides, and horizontal ; the pore-area more markedly tuberculiform. Phallopods 
with distal segment lightly arcuate, the inferior edge convex and hairy, the upper concave and smooth, 
ending in three processes—a median large, apically laminate and compressed, with sinuously rounded 
edge, which carries the seminal duct, and a shorter one on each side, the inner of the two narrowed and 
pointed, with two small teeth above, the outer more bluntly rounded, but with a short angular process 
above. 
Length, 9, 30 millim., width 5. 
9» 6,45 5 » 2 
Hab. Mexico *, plateau of Puebla, Peak of Orizaba, and Volcan de Tuxtla! ?. 
