THE 



GEOLOGICAL MAGAZINE 



NEW SERIES. DECADE VI. VOL. V. 



No. III.— MARCH, 1918. 



OJEiIC3-II<r.A.L .A.I?,TI031.E]S. 



I. — Notes on new or impehfkctly known Chalk Poltzoa. 



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



{Continued from the January Number, p. 4.) 



(PLATE VI.) 



Pseudostege concursa,^ sp. nov. (PI. VI, Figs, 1-3.) 



Zoariutn incrusting, with a tendency to grow in bands : the 

 general surface stands high and shows no trace of zooecial boundaries ; 

 it is much rumpled, apparently unsysteraaticaUy, but is only 

 broken by the zocecial peristomes; these are short tubular 

 prominences inclined sligbtly forwards but bent upwards at the 

 ends so as to end in a plane parallel with the general surface : the 

 apertures are on the whole circular, but very rarely truly so, and 

 occasionally very irregular; they vary in internal diameter from 

 •08 in a small specimen such as Fig. 2 up to "15 mm. in a large 

 specimen such as Fig. 3 ; the peristomes are thick and each has 

 from one to four pores in it ; these pores are generally small and 

 round, but occasionally among the larger ones are found definite 

 instances of arrowhead shape which makes it possible that all are 

 avicnlariaii : round the edges of the zoarium there is a fairly 

 complete fringe of simple shallow Membraniporiform zooecia, with the 

 general surface either ending abruptly above them or sloping gradually 

 down to them. 



Ocecia small and globose, perched on or sunk slightly into the 

 anterior part of the peristome, very erratic in occurrence. 



Avicularia of two kinds — {a) accessory, as above described, 

 (5) vicarious, of liour-glass type with the upper lobe much elongated, 

 the lower very short and devoid of internal front wall and indications 

 of a transvei'se bar at tlie point of maximum constriction; these 

 occur at or near the edge of the zoarium. 



This species is referred only provisionally to Pseudostege, as I do 

 not feel confident that the fringe of Membraniporiform zooecia 

 really represents a primary stage, nor am I clear as to how exactly 

 the general zoarial crust is developed. The species is introduced 

 here because it occurs at the same horizon in Hants, about the 

 junction of the zones of A. quadratus and £. mucronata, as several of 

 the Memhraniporell(B I have just been describing, and presents so 



^ The term Pseudostega has been used for a division of the Cheilostomata, 

 .presumably as a neuter plural. This term is not therefore identical with my 

 g&nxx^ Pseudostega (Geol. Mag., 1910, p. 259), which is a feminine singular, 

 but to avoid any risk of confusion it is perhaps as well to amend my term to 

 Pseudostege. 



decade VI. — VOL. V. — NO. III. 7 



