GRAPTOLITES OF AUSTRALIA 
69 
problem of tbe development of branching forms such as 
Loganograptus and Dichograptus is complicated in Victoria 
by the simultaneous appearance of so many variants in the 
one bed without any indication of them in lower zones. It 
is therefore impracticable as far as Victorian graptolites are 
concerned to account for the production of Dichograptus by 
the reduction of stipes of Loganograptus unless it is pre- 
sumed that reduction commenced as soon as Loganograptus 
appeared. The two forms appear together in B5, Dichograp- 
tus then persists, though not as a common form, as high as 
the Middle Darriwil, while Loganograptus is hardly known 
to occur again (one or two specimens have been recorded) 
until the Upper Castlemaine zones are reached, in spite of 
the large collections that have been made from intervening 
horizons. We have already referred to five- and six-branched 
dependent forms, which in number of branches, resemble 
Tetragraptus fruticosus, the normal four-branched form of 
which also occur in the same bed. These forms, abnormal 
in nothing except in number of branches, we must by current 
usage separate as Bryograpti (vide B. crassus infra). 
Another example of reduced branching is shown by forms 
from the B5 and B4 horizons which have only three branches 
and have therefore a superficial resemblance to Triograptus 
Monsen. It seems clear, however, that the three-branched 
habit is not due to the typical Triograptus form of develop- 
ment but rather to the failure of a fourth branch to arise in 
a horizontal Tetragraptus such as T. harti; that is these 
forms represent the three-branched phase of a horizontal 
Tetragraptus in the same way as the three-branched T. 
fruticosus does of a dependent Tetragraptus. An alternative 
would be to derive them from Trichograptus by suppression 
of branches but the Tetragraptus explanation seems 
simpler.” Specimens were figured in the present paper but 
the authors postponed fuller discussion. 
The forms figured and described are: Trocliograptus aus- 
tralis, sp. nov., T. indignus sp. nov., T. cf. diffusus, Schizo- 
graptus incompositus sp. nov., S. spectabilis sp. nov., Sigma- 
graptus yandoitensis sp. nov., Trichograptus fergusoni, 
Bryograptus crassus sp. nov., Clonograptus rarus sp. nov., 
C. smithi sp. nov., C. ramulosus sp. nov., C. teneUus var. 
proUematica nov., Dichograptus sedecimus sp. nov., Tetra- 
graptus pendens, T. harti, T. triograptoides sp. nov., T. 
volitans sp. nov., T. approximatus, Didymograptus latus, D. 
latus var. aequalis nov., D. ahnormis, D. hemicyclus, D. 
similis, D. cf. suecicus, D. vicinus sp. nov. and D. aspersus 
sp. nov. 
