us_, _Slimonia_, _Stylonurus_ were
other genera.

Insects appear well developed, including both orthopterous and
neuropterous forms, in the New Brunswick rocks. Mr Scudder believed he
had obtained a specimen of Orthoptera in which a stridulating organ
was present. A species of _Ephemera_, allied to the modern may-fly,
had a spread of wing extending to 5 in. In the Scottish Old Red
Sandstone myriapods, _Kampecaris_ and _Archidesmus_, have been
described; they are somewhat simpler than more recent forms, each
segment being separate, and supplied with only one pair of walking
legs. Spiders and scorpions also lived upon the land.

The great number of fish remains in the Devonian and Old Red strata,
coupled with the truly remarkable characters possessed by some of the
forms, has caused the period to be described as the "age of fishes."
As in the case of the crustaceans, referred to above, we find one
assemblage more or less peculiar to the freshwater or brackish
conditions of the Old Red, and another characteristic of the marine
Devonian; on the whole the former is the richer in variety, but there
seems little doubt that quite a number of genera were capable of
living in either environment, whatever may have been the real
condition of the Old Red waters. Foremost in interest are the curious
ostracoderms, a remarkable group of creatures possessing many of the
characteristics of fishes, but more probably belonging to a distinct
class of organisms, which appears to link the vertebrates with the
arthropods. They had come into existence late in Silurian times; but
it is in the Old Red strata that their remains are most fully
preserved. They were abundant in the fresh or brackish waters of
Scotland, England, Wales, Russia and Canada, and are represented by
such forms as _Pteraspis_, _Cephalaspis_, _Cyathaspis_, _Tremataspis_,
_Bothriolepis_ and _Pterichthys_.

In the lower members of the Old Red series _Dipterus_, and in the
upper members _Phaneropleuron_, represented the dipnoid lung-fishes;
and it is of extreme interest to note that a few of these curious
forms still survive in the African _Protopterus_, the Australian
_Ceratodus_ and the South American _Lepidosiren_,--all freshwater
fishes. Distantly related to the lung-fishes were the singular
arthrodirans, a group possessing the unusual faculty of moving the
head in a vertical plane. These comprise t