4 R. M. Brydone—On Chalk Polyzoa. 
Puate II. 
Fic. 1. Thin slice (1459), magnified fifteen diameters. The two large dark grains 
with parallel cleavage lines are augite. That on the left extinguishes parallel to 
the cleavage and shows in convergent light an optic axis just outside the field of 
view, and is, therefore, parallel to (100). The lighter one at the left-hand 
bottom portion of the figure extinguishes at an angle of 5° with the cleavage 
cracks and shows only a slight trace of an axial figure. To the left and the right 
are several olivine grains. At the right-hand top corner is a small portion of the 
basalt in which the nodule occurs. 
Fic. 2. ‘Thin slice (1459), magnified twenty diameters, showmg the junction 
between a nodule and the basalt in which it occurs. In the nodule, in the upper 
part of the figure, olivine and augite are seen, and in the lower part the flow- 
structure of the felspar microlites in the basalt. 
Fic. 3. Thin slice (76), magnified fifteen diameters. Basalt containing phenocrysts 
of augite and olivine in a groundmass of felspar microlites of magnetite and glass. 
The big crystal of augite, to the left, contains inclusions from the groundmass 
zonally arranged. On the right is a small phenocryst of olivine. 
IJ.—Novrs oN NEW oR IMPERFECELY KNOWN CHALK Potyzoa. 
By R. M. Brypong, F.G.S. 
(PLATE III.) 
(Continued from Vol. VI, p. 400.) 
Mrmpranipora HuMILIATA, noy. Pl. III, Figs. 1-3. 
Zoarium always adherent. 
Zoecia generally elongated, but very variable in shape and dimen- 
sions; length of area ‘68 to -48 mm., breadth of area -386 to -2 mm. ; 
no front wall, side walls very low, with a further depression at the 
head of the zocecium, and furnished all round with slender buttresses, 
whieh are much more easily distinguished in the upper part of the 
zoecium, owing to their greater size and projection there, than in 
the lower part. 
Owcia semi-elliptical in outline, relatively very small, very frequently 
present, very brittle and especially so when associated with avicularia, 
so that zocecia with typical arrangement of perfect ocecium succeeded 
by avicularium are exceedingly rare. 
Avicularia accessory, small oval rings lying at the head of the 
zocecium and normally symmetrically above the ocecium when present, 
but sometimes beside it. 
The species is easily distinguished by the abnormal shallowness of 
the zocecia, which makes specimens look to the naked eye like much- 
worn remains of other species, and causes such inequalities in the 
underlying surface as the smaller tubercles of Zchinocorys, which 
would be out of sight at the bottom of zocecia of normal depth, to 
show up most prominently. 
Fairly common at Trimingham. 
MEMBRANIPORA ANTERIDES, nov. Pl. III, Figs. 4-6. 
Zoarium always adherent. 
Zoecia pyriform with subtriangular area and considerable extent of 
front wall below it; length of area -32--36mm., width of area 
‘2-24 mm.; side walls supported by buttresses; at the head of the 
