SHOWING STRUCTURE, FROM THE RHYNIE CHERT BED, ABERDEENSHIRE. 875 
the Filamentous Bacteria. No satisfactory evidence of septation or of the presence 
of bacterial cells within the tubular sheath has been obtained. Under certain con- 
ditions of preservation the latter contains dark granules, but the arrangement of 
these is too irregular to afford a safe indication of any original structure. 
The organism is so well marked in appearance and mode of occurrence that it is 
recorded and figured here, but, as pointed out above, its systematic position must be 
regarded as somewhat uncertain. It is. suggested below (p. 876) that it may be 
referred to provisionally by the name Archseothrix contexta. 
Schizophyta No. 3. Archseothrix oscillatoriformis. (PI. VIII, figs. 89 and 90.) 
A remarkably well-preserved organism that can only be placed in the Schizophyta 
is represented in figs. 89 and 90. It was found in a large cavity due to decay in a 
stem of Rhynia Gwynne-Vaughani in the form of a number of slender unbranched 
filaments. Two groups of these are seen at a and b in fig 89, and above group a 
a long undulating filament is very clearly shown. A portion of this latter filament 
is represented more highly magnified in fig. 90. The way in which some of the 
filaments were curved back on themselves contrasted with the behaviour of fungal 
hyphse, some of which were also present in the cavity. The filaments (fig. 90) were 
divided into numerous short discoid cells, the protoplasts of which have persisted 
and been preserved. 
The structure of this remarkable organism may be most closely compared with 
such existing plants as slender forms of Oscillatoria ; it agrees with these in the 
short disc-like cells and in the curvature of the unbranched filaments. It is, how- 
ever, also comparable with the slender colourless filaments of such existing Bacteria 
as Beggiatoa, and it is generally recognised that there is much in common between 
the Oscillatoriacese and the Beggiatoaceae. Though it is, of course, impossible to tell 
whether the fossil plant was green or colourless when alive, its systematic position 
appears to be clear. It is noteworthy that in this specimen it is the protoplasts or 
cell-contents that have persisted — a mode of preservation that is unlike that of the 
fungi in the same bed of the deposit. This feature as well as the general appear- 
ance seems to be in favour of regarding this organism as one of the Cyanophycese. 
Archseothrix , n.g., Kidston and Lang. 
Slender unbranched filaments suggesting close comparison with Filamentous 
Cyanophycese or Filamentous Bacteria. 
Archseothrix oscillatoriformis, n.sp., Kidston and Lang. (PI. VIII, figs. 89 and 90. 
Slide No. 2542.) 
Unbranched filaments, often curved ; about 3-4 v- in diameter. Within a sheath- 
like outer wall are the preserved protoplasts of the small discoid cells. 
