PERIPATUS. 335 
in the Devonian period, it is reasonable to suppose that other 
insects, besides Hemiptera and Blattids, must have inhabited 
the dry land of the Silurian period. 
While true scorpions have been found in the Upper Silu- 
rian rocks of Scotland, Sweden, and New York, the oldest 
insect-remains are the wing of Palwodlattina douvillei, an 
insect probably allied to the cockroach, and found in the 
Middle Silurian rocks of France. ; 
In the Devonian of St. Johns, N.B., have been discovered 
fragments of the wings either of a May-fly or dragon-fly, and 
five other species of doubtful position. 
In the Carboniferous formation insect-remains are more 
numerous; they belong to the Thysanura, Orthoptera, May- 
flies, dragon-flies, Hemiptera, with composite forms (Huge- 
reon) and genuine Newroptera, allied to Stalis and Corydalus. 
No insects with a complete metamorphosis (except the Meu- 
roptera) are yet known to have lived before the Mesozoic age. 
Crass III].—Matxacopopa (Peripatus). 
Characters of Malacopoda.—This group is represented by 
a single animal, the strange Peripatus of tropical coun- 
tries, in which the body is cylindrical, the integument, an- 
tenne, and limbs soft, not chitinized, with the head not 
separate from the body, and bearing a pair of many-jointed 
extensible antenne, with two pairs of rudimentary jaws 
{mandibles and maxille), ahd from fourteen to thirty-three 
pairs of feet. There is a pair of nephridia to each segment. 
It differs from other Arthropods in the two widely separated 
minutely ganglionated nervous cords sent backward from the 
brain; also in the minute, numerous tracheal twigs arising 
from numerous minute oval openings (rudimentary spiracles) 
situated irregularly along the median line of the ventral 
surface of the body. The feet are soft, fleshy, and end in 
two claws. Peripatus is viviparous. According to the 
description and figures of Mr. Moseley, the young develop 
much as in the chilopodous Myriopods (Greophilus), show- 
ing that Peripatus is nearer to the Myriopods than any 
other group. That it is a tracheate animal was also proved 
by Mr. Moseley; but owing to the nature of the nervous 
system, the minute trachee and their numerous irregular 
