IJYTHOTREPHIS IN VICTORIA. 
OX AN ADDITIONAL OCCUEKENCE OE BYTHOTREPHI8 
IN VICTORIA. 
By A. H. 8. Lucas, M.A., B.8c. 
(Plate XIV.) 
1 am indebted to the autliorities of the National Museum, Mel- 
bourne, for tbe opportunity of describing tlie following specimen. 
Presumably tlie primitive flora of the world was entirely algal. 
Other forms appear to have developed from different types of 
algae. Hence it is of interest and imjiortance to ascertain what 
types of algae flourished in the earlier times, how they were dis- 
tributed, and what was their elemental structure. The evidence 
is fragmentary, and owing to the soft entirely parenchymatous 
nature of the plants but little of the structure has been preserved 
and revealed. The occurrence, then, of a specimen of a well grown 
alga in beds so adapted to the preservation of soft parts that a 
jelly-fish is shown in nearly its entirety in them, gave hopes that 
information of value might be furnished as to early algal structure. 
Lhifortunately very little has been gained so far in this regard, but 
it is interesting to find an alga in the Melbournian Beds of Victoria, 
apparently identical with one from the Lower Ordovician of North 
America. 
The fossil consists of two main fronds of Dictyota habit wliich 
diverge as if proceeding from a common attachment. They do 
not lie flat in one plane but are extended freely as on an undulated 
surface, seemingly showmig that they were imbedded in rapidly 
accumulating sediment. One often finds recent ])lants like Dictyota 
dichotoma similarly half sunk in wet sand which has been pouretl 
over them by the tide succeeding that which deposited them on 
the beach. The fronds are com])ressed, repeatedly dichotomous, 
with acute axils, the segments not rapidly diminishmg in width. 
Length of frond 78 mm., while the spread of the two fronds occupies 
a width of 94 mm. Tlie width of the segments average about 3 
mm. The length of the longest branch 60 mm. The substance 
is carbonaceous. A collodion film showed rounded cells loosely 
grouped with rather thin borders, 79-124/x in diameter (pi. XIII., f. 3). 
I venture to identify the form with Bytiiotmidiis ymcilis, James 
Hall, described and figured from the Trenton Limestone, in the 
upper part of the Lower Ordovician of New York.^ 
Hall’s description is as follows : — 
“ Form slemler, flattened, branched ; branches com- 
pressed, leaflike, subdichotomous, diverging, opposite and 
alternate ; no visible structure. 
1 Palaeontology of Netv York, Vol. p. G2, Plate XXI., lig. 1, Albany, 1847. 
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