THE 
GEOLOGICAL MAGAZINE, 
NEV SERIES: “DECADE Vi (VOLES VITT™ 
No. XI.— NOVEMBER, 1910. 
ORIGINAL ARTICLIEHMS- 
i 
I.—Norrs oN NEW OR IMPERFECTLY KNOWN CHALK Potyzoa. 
By R. M. Brypons, F.G.S. 
(PLATE XXXVI.) 
(Continued from the September Number, p. 392.) 
STEGINOPORA DENTIcULATA, noy. Pl. XXXVI, Figs. 1-3. 
Zoarium always unilaminate, nearly always adherent. 
Zoeecia broad, length -65-"8 mm., breadth -45--55 mm., aperture 
primarily semicircular but tending to quadrangular by thickening of 
the upper lip, and with a semicircular collar, the two ends of which 
are expanded into large perforated spine bases: the arched front wall 
springs from the inside of the side walls and is pierced along its edge 
by a row of large pores, and at a short distance inside this row by 
a row of smaller pores in fairiy close correspondence with the outer 
row; the centre of the front wall is pierced by a very variable 
number of fine pores, which sometimes give clear indications of 
a third row corresponding to the two outer ones; the zocecia always 
have common side walls of considerable width; in immature stages 
(Fig. 1) the front walls rise high above the side walls, and small beak- 
shaped avicularia are scattered irregularly between them; in a further 
stage of development (Fig. 2) the side walls are greatly thickened 
and raised above the front walls, absorbing the avicularia, and the 
perforated spine bases at the corners of the aperture grow inwards 
until they meet, and are fused into a stout bar across the aperture, so 
qualifying the species for admission to the Steginoporide; in the 
stage of maximum development (Fig. 3) the bar develops a stout 
denticle in the middle of the lower edge. 
Oecia not observed. 
Rare in the zone of I. cor-anguinum at Gravesend, Broadstairs, 
Kingsgate Bay, and Leaves Green, near Bromley. 
Srecinopora GRAvENsSIs, nov. Pl. XXXVI, Figs. 4-5. 
Zoartum unilaminate, adherent. 
Zoecia long and narrow, average length ‘65 mm., breadth ‘35--4 mm.; 
with very broad common side walls, between which is deeply sunk 
the flat front wall pierced by numerous transverse paired slits, which 
DECADE V.—VOL. VII.—NO. XI. 31 
