The sub-class Arachnida are at once recognized by their eight legs.
A Monograph of the sub-class Cirripedia, with figures of all the species.
The first sub-class consists of the Hags (Hyperotreta, or Myxinoida).
The Hydromedusae represent, therefore, a sub-class of the Hydrozoa.
Each 'phratry' then bartered a sub-class of its own for a sub-class of its partner.
At this time, too, appeared the earliest Reptiles, chiefly of the Amphibia sub-class.
Hence the name of the sub-class signifying tri-lobed, a condition realized also in the Xiphosurous Arachnids.
Thus they belong to the sub-class, the members of which have a raft-like breast bone.
The sub-class of the Hydrozoa, which comprises the animals most nearly allied to the Hydra.
To a sub-class selected for a centre, two qualities are indispensably requisite.