188 
Joan M, Crockforb, M.Sc. 
Infundibuliform or flabellate Fenestrellinidae, with two rows of alternating 
zooecia on the branches, except before bifurcation, when the number of rows is 
increased ; rows of zooecia separated by a median carinn, plain or more fre- 
quently with a single row of nodes {acantho pores) ; dissephnents not cellnliferous; 
internal structure and reverse surface as for the family. 
Fenestrellina affluensa (Bretnall). 
(Plate I., fig. 6.) 
Fenestella affluensa Bretnall, 1926, W.A. Geol. Survey, Bull. 88, p. 16, 
pi. I., fig. 8. 
Fenestella affluensa Bretnall, Hosking, 1931, Jour. Roy. Soc. W.A., Vol. 
XVII., p. 12. 
Lectotype : Specimen 2 /2405E, Western Australian Geological Survey 
Collection ; on specimen figured by Bretnall, 1926, pi. III. 
Horizon and locality ; Between the top of the Lyons Series and the top 
of the Byro Series, Gascoyne River District, W.A. 
Fenestrellina with three to four zooecia to a fenestride ; carina slight, 
rounded ; nodes large. 
The form of the colony is not shown ; the lectotype is about Do cm. 
long and D1 cm. wide. There are from 12 to 14 branches horizontally, and 
8 fenestrules vertically, in 10 mm. ; the branches are straight, normally from 
about 0'4 to 0*53 mm. in width, but rather narrower — about 0*35 mm. — 
where they are slightly weathered ; on the celluliferous surface the carina is 
poorly developed, being represented only by a I’ounded area free from ceils 
along the centre of each branch, sej)arating the two rows of alternating cell 
apertures. Nodes are wdl developed, but are only shown where the surface 
is best preserved ; they arc very large and blunt, and are slightly elongated 
parallel to the length of the branch ; theii’ width at the top is up to 0*33 mm., 
and the distance between the centres of successive nodes is from 0*68 to 
0*86 mm. The apertures are normally circidar, about 0*14 mm., in diameter, 
but they may be much enlarged by weathering ; they do not generally project 
into the fenestrules. Thin, raised peristomes are shown where the sui-face 
is well-preserved. The distance between the centres of successive apertures 
is from 0*29 to 0*37 mm., and about thirty occair in 10 mm. The fenestrules 
are oval — the dissepiments expand considerably at their junction with the 
branches — and are from 0*85 to 1*2 mm. in length and from 0*3 to 0*5 mm. 
wide ; the width of the dissepiments is from 0*25 to 0*36 mm. Bifurcation 
occurs at rather distant intervals, and increase to three rows of zooecia occiirs 
just before branching. The thickness of the branches is about 0*65 mm. 
In specimens from the same locality, but not sjmtypes, the reverse surface 
shows a number of fine longitudinal striae where it is slightly weathered ; 
the dissepiments are very nearly as thick as the branches, and both are evenly 
rounded. 
Remarks : There are three specimens labelled “ 17 ” (the number given 
by Bretnall as that of the holotype) in the collection ; of these the largest 
and best preserved is here chosen as the lectotype, and the measurements 
given in the above description were taken on it ; there is a second, very small 
specimen on the same piece of shale, and a third, very much weathered speci- 
men on a piece of limestone from the Callytharra Stage at Fossil Hill, Wyndham 
River. Both of these show fenestrules slightly longer than the average shown 
