SELLARDS. | Cockroaches. 503 
sects will be found ultimately in both Permian and Coal Meas- 
ures deposits of Kansas. 
The Kansas collections are rich in immature, or nymph, 
cockroaches. Bodies of adult cockroaches are seldom pre- 
served, not a single specimen occurring among the Kansas 
collections, although not less than 107 nymphs or parts of 
nymphs are present. These are in most, perhaps in all, cases 
the molts or cast off integuments of nymphs. The molts are 
lighter, float more readily, escape the danger of being eaten 
by insect-feeding animals, resist decay, and are in every way 
better adapted for preservation than are the soft bodies of 
adults. 
The body structure of the Paleoblattide is, so far as known, 
essentially the same as that of modern cockroaches. The body 
has the same flattened form; the small head usually hidden by 
the rounded pronotum; antennz seldom complete, but evi- 
dently long and slender; eyes, so far as can be seen in the 
fossil condition, like those of modern forms; the mouth-parts 
apparently have failed of preservation; of the legs the coxa 
and trochanter are occasionally seen, the femur and tibia more 
often; the more delicate tarsus, however, is indistinctly pre- 
served; the tibia, in some species at least, is spinous; in other 
species evidence of spines is lacking; the abdomen is broadest 
at the middle; the ten terga in the nymph stages of both male 
and female are distinct; the first tergum is small, about as 
board as long; the following increase in length up to the fourth 
or fifth, where the abdomen is broadest, beyond which the 
abdomen narrows to the rounded tenth tergum; the cerci pro- 
ject from beneath and at the side of the tenth tergum; the 
sterna, partly covered by the terga, are less definitely known; 
occasionally sterna three to nine are seen, evidently little 
modified, lying beneath their respective terga. These indi- 
viduals are without doubt males. Others (females, as shown 
by the presence of the ovipositor) have a much enlarged 
seventh sternum lying beneath the seventh, eighth and a part 
of the ninth terga. A striking feature seen on some Paleozoic 
nymphs is the presence of a straight or sword-shaped ovi- 
positor projecting from the abdomen, in some genera as long 
as the abdomen itself. As seen in the later nymph stages the 
parts of the ovipositor are closely united, the whole appearing 
as a straight resistant organ projecting from beneath the terga 
and from above the sterna. A young nymph of Htoblattina 
