A REVISION OF SOME PREVIOUSLY DESCRIBED SpECIES OF BRYOZOA 191 
FROM THE Upper Palaeozoic of Western Australia. 
Lyropora Hall, McNair, 1937, Michigan University Museum of Paleojitol- 
ogy Contributions, Vol. V., No. 9, p. 114. 
Genotvpe (selected bv Ulrich, 1890) : L'tiropora subquadravs (Hall), 
1857 (L. lyra (Hall), 1857). 
Synonyms : — 
Dictyoretmon Whitfield, 1904. 
Lyroporella Simpson, 1895. 
Lyroporina Simpson, 1897. 
Zoariuni fenestrate ; colony flahellif or m, with the sides near the base strongly 
thickened to form the lateral supports ; brayiches with two or more rows of zooecia, 
dissepimemts without zooecia ; reverse swface and internal structure as in Fenos- 
trellina. 
Lyropora erkosoides (Etheridge). 
(Plate I., fig. 2 ; plate II., fig. B.) 
Lyropora (^) erkosoides Etheridge, in Bretnall, 1920, W.A. Geol. Survey, 
Bull, 88, p. 11, pi. II., figs. 1, 4. 
Lectotype : Specimen 2 /2404, Western Australian Geological Survey 
Collection; figured by Bretnall, 1926, pi. II., fig. 1. 
Horizon and locality ; Callytharra Stage (?), Well A 20, Daiirie Creek, 
Gascoyne River District, Western Australia. 
Lyropora with two rows of zooecia, and two zooecia to a fenestride ; carina 
slight . nodes sharp, high, evenly spaced. 
The zoarium is flabellate ; the base is small and pedunculate, and the 
sides of the colony above the base are strongly thickened, and form the lateral 
supports characteristic of the genus. These lateral supports diverge at an 
angle of about 70°, and the zoarium is celluliferous on the convex surface ; 
the holotype reaches a height of 4 cm. above the base, and a width, at the 
top, of about 4 cm. There are about 22 branches horizontally, and 18 fenes- 
trules vertically, in 10 mm, The branches are straight, and are usually from 
0*22 to 0*29 mm. in width, but they become much broader towards the sup- 
ports, and before bifurcation. There are two rows of zooecial apertures, 
separated by a very slight median carina on which there is a single row of 
high nodes, rather elongated along the carina at their bases. The nodes are 
placed from 0*3 to 0*37 mm. apart. The apertures are circular, about 
0*09 mm. in diametei' ; slight peristomes arc shown — these are best developed 
on the side towards the fenestrules. There are two apertures to a fenestrule, 
and over part of the specimen these are arranged so that one is opposite the 
end of each dissepiment, and one at the centre of each fenestrule, giving the 
fenestrules an hour-glass shape ; over most of the specimen, however, the 
arrangement is not regular, and the fenestrules are oval in shape. The dis- 
tance between the centres of successive apertures is from 0-24 to 0-32 mm., 
and about thirty-seven occur in 10 mm. The fenestrules are from 0-35 to 
0-46 mm. in length, and from 0*17 to 0-29 mm. — generally about 0*2 mm. — 
in width ; the width of the dissepiments is from 0-13 to 0-21 mm. On the 
reverse surface both branches and dissepiments are evenly roimded, and 
they are of about the same thickness — their thickness varies, however, with 
the distance from the lateral supports. The outer layer of the reverse surface 
is finely granular ; within this a few fine longitudinal striae are shown. Bi- 
furcation occurs at very distant intervals, and increase to three rows of zooecia 
occurs just before branching. 
