GRARTOLITES OP VICTORIA. 
Period 
Series 
Darriwilian 
Castlemainian . . 
i 
Lower Ordovician . . . . . . j 
Bendigonian 
Lancefieldian 
Family DICHOGRAFTIDAE Lap worth 1873. 
Zonks. 
D1 
D2 
D3 
D4 
D5 
[Cl 
C2 
■ C3 
C4 
C5 
(B1 
B2 
B3 
B4 
B5 
(LI 
L2 
L3 
L4 
L5 
Genus DIDYMOGRAPTUS McCoy 1851. 
Didymograptus acriculus, sp. nov. 
(Plate XX, Figs, la, lb, and Text tig. 1.) 
Branches several centimetres in length ; incomplete ; less than 0.5 mm- 
wide at origin but widens rapidly (at 3.5 mm. from sicula 2.0 mm. wide) to 
3.5 mm. ; diverging from inconspicuous sicula at slightly more than 180° but 
rapidly becoming horizontal. 
kyax b 
Fig. 1. Didymograptus acriculus, sp. nov. 
a. Distal thecae (No. 23507). b. Proximal thecae (No. 22811). X4. 
Thecae, in proximal portion, 10 or 11 in 10 mm. ; inclined at 30 ; over- 
lapping about half of length. In distal portion, thecae 7 in 10 mm. , inclined 
at 50° ; overlapping two-thirds of length ; three times as long as wide ; ventral 
margins doubly curved ; apertural margins sigmoidal, at 95° to axis of branch 
and produced into broad, conspicuous denticles. 
[167] 
