CYCLODESMUS.—SPH ERIODESMUS. 119 
Third segment much the largest of the series ; its keels greatly expanded. Second segment crescentic ; 
anal tergal plate broad, quadrate. 
Distribution. Mexico and Jamaica. 
1. Cyclodesmus aztecus. 
Cyclodesmus aztecus, Sauss. & Humb. Rev. et Mag. Zool. 1869, p. 149°; Miss. Sci. Mex., Myr. 
p. 24, t. 1. fig. 8 (1872) *; Carl, Rev. Suisse Zool. x. p. 678, t. 12. fig. 109 (1902) °*. 
Colour white. General form like that of Sphariodesmus, but the body compressed and attenuated posteriorly. 
Keels of second segment not surpassing the lateral angles of the first. Keels of the third with convex 
anterior and concave posterior borders ; acute posterior and widely rounded anterior angle. Keels of 
fourth segment only a little larger than those of the fifth, rounded inferiorly. In the mid-region of the 
body the keels have straight and vertical posterior borders and rounded angles, but in the posterior half 
they are directed slightly backwards, with oblique posterior borders and acute posterior angles. 
Length 5-6 millim., width 1-6. 
Hab. Mexico, Eastern Cordillera ! °. 
Subfam. SPHARIODESMINA. 
The three described genera of this group, if Colobodesmus be admitted, may be 
contrasted as follows :— 
a. Orifice of seminal duct of phallopod on a low eminence situated far behind 
the distal end of that organ. . 2. 1. we ew ee ew ee ee) )~6COLOBODESMUS. 
a’. Orifice of seminal duct of phallopod on a longer or shorter process at or near 
the apex of the phallopod. 
b. Posterior ventral border of segments, at least in posterior half of body, 
straight and transverse ; the anterior tubercle remote from the base of 
the leg ; keel of fifth segment markedly smaller than that of fourth . . Cy.ionus. 
6’. Posterior ventral border of segments strongly convex or angled internally, 
oblique and concave externally ; keel of fifth segment not smaller than 
that of fourth. 2. 2. 1 wee we ee we ew eee «06S PHERIODESMUS. 
SPHAERIODESMUS. 
Glomeridesmus, Saussure, Linn. Ent. xii. p. 328 (1858); Mém. Soc. Phys. Genéve, xv. p. 276 
(1860) (nec Glomeridesmus, Gerv.). 
Spheriodesmus, Peters, Mon. Ak. Wiss. Berlin, 1864, p. 529, and of subsequent authors. 
Characters as above. 
Distribution. Central America. 
Although females of the species of this genus may usually, at all events, be 
distinguished by slight differences in the shape of the body, some being more arched 
than others, especially at the posterior end, some broader, some narrower, by differences 
in the size and shape of the keels, by differences in the length of the individual 
segments of the antenne and legs, and by the hairiness of these appendages, these 
