THE 
GEOLOGICAL MAGAZENE: 
NEW SERIES. DECADE VI. V tM, 
antl Se Ree es A 1Q1h 
No. X—OCTOBER, 1916. = OCT 241910 
ORIGINAL Se a mus? ew 
———— 
I.—Norzs ON NEW OR IMPERFECTLY KNOWN CHALK Pauwaone 
By R. M. Bryponz, F.G.S. 
(Continued from the August Number, p. 3389.) 
(PLATE XVIII.) 
HEILOSTOMATOUS Polyzoa are anything but common in the 
Chalk exposed on the Norfolk coast between Cromer and Wey- 
bourne, and which I will call the Weybourne Chalk as it is best 
exposed in the Weybourne half of the area. It was only quite 
recently that I realized that the gradual accumulation of material 
had produced a sufficient volume to give some idea of the general 
nature of the fauna. The precise position of this chalk in the zone 
of B. mucronata cannot be fixed on physical data, but the Survey 
view that it is only a little way below the Trimingham Chalk is 
highly probable. It is therefore rather remarkable to find that the 
Membranipore include several new species, in addition to IZ. flacilla 
(ante, p. 3388), which are unknown so farat Trimingham. It will be 
interesting to see if these, which I proceed to describe, prove to be 
characteristic of any definite range of chalk in the Norfolk Senonian. 
They must all be described as scarce at Weybourne. 
MEMBRANIPORA FLUONIA, Sp. nov. (Pl. XVIII, Figs. 1 and 2.) 
Zoarium unilaminate, adherent. 
Zoeca strongly pyriporiform, very large; ‘9mm. is an average 
length in the centre of the zoarium, and the marginal zocecia frequently 
run to such lengths as 1-2 mm.: areason the whole broadly elliptical, 
but varying from broadly oval to practically circular, with lengths 
varying from an average of ‘45 mm. in the centre of the zoarium up 
to ‘6mm. at the margin; they occupy the bottom of cups formed by 
the internal front walls, which are of considerable width, and have 
a markedly prismatic structure, and are separated from the convex 
external front walls by a ridge which though obtuse-angled is often 
quite sharp. 
Oecva prominent, sub-conical, with a slightly contracted base; free 
edge moderately concave. 
Avicularia sub-vicarious, initiating néw rows of zocecia, large and 
of hour-glass type with remains of a crossbar well below the region 
of constriction, and the area narrowly lancet-shaped at the upper end. 
DEOADE VI.—VOL. III.—NO. X. 28 
