ian scorpion are the legs of an aquatic Arthropod, such as a crab
or lobster. It is probable that the Silurian scorpion was an aquatic
animal, and that its respiratory lamellae were still projecting from
the surface of the body to serve as branchiae. No trace of "stigmata,"
the orifices of the lung-chambers of modern scorpions, can be found in
the Scottish specimen of _Palaeophonus_, which presents the ventral
surface of the animal to view. On the other hand, no trace of
respiratory appendages excepting the pectens can be detected in the
specimen (see fig. 49).

[Illustration: FIG. 50.--Comparison of the sixth prosomatic limb of a
recent scorpion (B), of Palaeophonus (C), and of Limulus (A), showing
their agreement in the number of segments; in the existence of a
movable spine, Sp, at the distal border of the fifth segment; in the
correspondence of the two claws at the free end of the limb of Scorpio
with two spines similarly placed in Limulus; and, lastly, in the
correspondence of the three talon-like spines carried on the distal
margin of segment six of recent scorpions with the four larger but
similarly situated spines on the leg of Limulus; s, groove dividing
the ankylosed segments 4 and 5 of the Limulus leg into two.

(After Pocock, _Q. J. Mic. Sci._, 1901.)]

[Illustration: From Lankester, _Journ. Linn. Soc. Zool_. vol. xvi.,
1881.

FIG. 51.--Drawing from life of the desert scorpion, _Buthusaustralis_,
Lin., from Biskra, N. Africa.]

Fossil scorpions of the modern type are found in the Coal Measures. At
the present day scorpions of various genera are found in all the warm
regions of the world. In Europe they occur as far north as Bavaria and
the south of France. The largest species measure 9 in. from the front
of the head to the end of the sting, and occur in tropical India and
Africa. Between 200 and 300 species are known. The scorpions use their
large chelae for seizing prey and for fighting with one another. They
never use the sting when (as frequently happens) they attack another
scorpion, because, as was ascertained by A.G. Bourne (24), the poison
exuded by the sting has no injurious effect on another scorpion nor on
the scorpion itself. The stories of a scorpion stinging itself to
death when placed in a circle of burning coals are due to erroneous
observation. When placed in such a position the scorpion faints and
becomes inert. I