sth 1, First or genital somite of the opisthosoma.
ge, Site of the genital aperture.
st, Thoracic tracheal aperture.
l^2, Anterior tracheal aperture of the opisthosoma in somite 2 of the
opisthosoma.
l^3, Tracheal aperture in somite 3 of the opisthosoma.
a, Anus.

(From Lankester, "Limulus an Arachnid.")]

[Illustration: FIG. 67.--_Galeodes sp._, one of the Solifugae. Ventral
view with the appendages cut off at the base.

I to VI, Prosomatic appendages.
s, Prosomatic stigma or aperture of the tracheal system.
1, First opisthosomatic sternite covering the genital aperture g.
2, Second opisthosomatic sternite covering the second pair of
tracheal apertures sp1.
sp2, The third pair of tracheal apertures.
10, The tenth opisthosomatic somite.
an, The anal aperture.

(Original by Pickard-Cambridge and Pocock.)]

[Illustration: FIG. 68.--_Galeodes sp._, one of the Solifugae. Dorsal
view.

I to VI, Bases of the prosomatic appendages.
o, Eyes.
a, Lateral region of the cephalic plate to which the first pair of
appendages are articulated.
b, Cephalic plate with median eye.
c, Dorsal element of somites bearing third and fourth pairs of
appendages.
d, Second plate of the prosoma with fifth pair of appendages.
e, Third or hindermost plate of the prosoma beneath which the sixth
pair of legs is articulated.
1, 2, 9, 10, First, second, ninth and tenth somites of the
opisthosoma.
an, Anus.

(Original.)]

_Galeodes_ has been made the means of a comparison between the
structure of the Arachnida and Hexapod insects by Haeckel and other
writers, and it was at one time suggested that there was a genetic
affinity between the two groups--through _Galeodes_, or extinct forms
similar to it. The segmentation of the prosoma and the form of the
appendages bear a homoplastic similarity to the head, pro-, meso-, and
meta-thorax of a Hexapod with mandibles, maxillary palps and three
pairs of walking legs; while the opisthosoma agrees in form and number
of somites with the abdomen of a Hexapod, and the tracheal stigmata
present certain agreements in the two cases. Reference to literature
(36).

[Illustration: FIG. 69.--_Galeodes sp._, one of the Solifugae.

I to VI, The six prosomatic limbs cut short.
o, The eyes.
b, c, Demarcated areae of the cephalic or first pros