the Cenimagni (i.e. "the Great Iceni" as they were still called,[46]
though their power was on the wane), East Anglia; while the
Cateuchlani, already beginning to be known as the Cassivellauni (or
Cattivellauni), presumably from their heroic chieftain Caswallon (or
Cadwallon),[47] corresponded roughly to the later South Mercians,
between the Thames and the Nene. The Segontiaci, Ancalites, Bibroci,
and Cassi were less considerable, and must evidently have been
situated on the marches between their larger neighbours. The name of
the Cassi may still, perhaps, cling to their old home, in the _Cashio_
Hundred and _Cassiobury_, near Watford; while conjecture finds traces
of the Ancalites in _Henley_, and of the Bibroci in _Bray_, on either
side of the Thames.

G. 3.--The Atrebates, who play a not unimportant part (as will be
seen in the next chapter) in Caesar's connection with Britain, were
apparently in possession of the whole southern bank of the Thames,
from its source right down to London--the river then, as in
Anglo-Saxon times, being a tribal boundary throughout its entire
length. This would make the Bibroci a sub-tribe of the Atrebatian
Name, and also the Segontiaci, if Henry of Huntingdon (writing in the
12th century with access to various sources of information now lost)
is right in identifying Silchester, the Roman _Calleva_, with their
local stronghold Caer Segent.

G. 4.--But the whole attempt to locate accurately any but the chiefest
tribes found by the Romans in Britain is too conjectural to be
worth the infinite labour that has been expended upon the subject by
antiquaries. All we can say with certainty is that forest and fen
must have cut up the land into a limited number of fairly recognizable
districts, each so far naturally separated from the rest as to have