THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE V. VOL. IX. 



No. X.— OCTOBER, 1912. 



I. — jN'otes on new ok imperfectly known Chalk Poltzoa. 



By E. M. Beydone, F.G.S. 



(Continued from the July Number, p. 296.) 



(PLATE XXII.) 



Membeanipoea pyeigeea, sp. nov. (PI. XXII, Figs. 1-5.) 



Zoarium always adherent, rarely large. 



Zooecia pyriform when not crowded, small, the earlier forms larger 

 than the later, but individually very variable ; area sub-triangular ; 

 a slight internal front wall, occasionally surrounded by a faint line ; 

 under the ooecia the rim is very thin, very low, and set distinctly back 

 from the general curve. 



Ooecia small, globose and prominent, the free edge coinciding very 

 nearly but not quite accurately with the general curve of the margin 

 of the area. 



Avicularia short and pyriform, with a narrow oval aperture in the 

 upper part deep-set within a short wide pyriform area, the sides of 

 which near its lower end are folded over and inwards into hour-glass 

 shape to a point which slightly overhangs the aperture; the rounded 

 upper end of the area is also bent upwards and inwards into a hood 

 sliaped like a flat meniscus. 



This species is one of the group of which M. confluens, Uss., is the 

 best known. It seems to be easily distinguishable by its avicularia 

 from any other described species. It is of regular occurrence 

 throughout the zone of^. quadratus and in the lower part of the zone 

 of B. mucronata ; and the form of the zone of M. cor-anguinum 

 illustrated by Pig. 4, and the form of the zone of Ifarsupites illustrated 

 by Pig. 5, are probably stages in its development. 



Membranipoea tenebrosa, sp. nov. (PL XXII, Pigs. 6-8.) 

 Zoarium always adherent ; all my specimens are quite small. 

 Zooecia very variable in size, more or less hexagonal, with a slight 

 tendency towards being sub-pyriform ; the area occupies the upper 

 half and is circular or nearly so, and lies at the bottom of a slight 

 circular depression, the rim of whicli is often marked by a faint line ; 

 a number of the zooecia, varying according to the state of preservation 

 and the care taken in cleaning, have smooth imperforate lids fitted to 

 the rims of these depressions, often so closely that no suture can be 

 detected, and the zooecium appears to have a perfectly smooth and 

 unbroken surface ; the lids are generally convex, but are sometimes 

 irregularly concave. 



DECADE V. — VOL. IX. — NO. X. 28 



