R. M. Brydone — New Chalk Pqlyzoa. 51 



Fig. 5 is the more typical, show how much variation is possible 

 within the species. v 



Cribrilina tumuliformis, sp. hot. (PI. Ill, Figs. 7 and 8.) 



Zoarium unilaminate, incru sting. 



Zooecia very variable in shape, but on the whole long and very 

 narrow for their length, like graves, often running to •7 mm. in length 

 with a breadth of only - 3 mm. ; no side walls visible : front wall 

 arched, with a sharply defined median ridge and numerous pairs of 

 imperforate furrows which are very faint but seem to run nearly up 

 to the median ridge; these furrows persist along the sides of the 

 aperture: aperture terminal and small in proportion, without any 

 thickened margin, almost circular with short and straight lower lip 

 and a sub-quadrate upper lip with very faint upper angles and a very 

 slight convergence to the lower lip ; sometimes the lower lip is 

 concave and the aperture is then practically circular ; a pair of tiny 

 tubercles occur at the upper angles, but are generally difficult to detect 

 except when they have been absorbed by the ocecia (for which they 

 act as starting-points) and re-exposed on the ocecia breaking. There 

 is a communication slit at the extreme upper end. 



Ocecia very abundant, elongated, slightly of the water-bottle type 

 (with a constricted neck just above the aperture), and slightly pointed 

 at the upper end, aperture small and semicircular, free edge distinctly 

 concave ; in a favourable light it can be discerned that these ocecia 

 are ribbed like the zocecia. 



Avicularia do not appear to occur. 



This species occurs sparingly in the 11. cor-anguinum zone and the 

 Uintacrinus band in Kent. It seems obviously an ancestor of 

 Cribrilina Filliozati, Bryd. 1 



Cribrilina Seafordensis, sp. nov. (PL III, Fig. 9.) 



Zoarium unilaminate, incrusting. 



Zocecia short and broad, average length - 4 mm. : no side walls 

 visible, but from broken specimens they appear to remain quite 

 distinct : front walls arched Avith numerous pairs of broad furrows, 

 all radiating, which nearly reach the middle line, but are quite 

 shallow and inconspicuous except near the margin, where they deepen 

 rapidly : aperture terminal, lower lip formed by the slightly 

 thickened terminal bar of the front wall, which is sometimes straight, 

 sometimes gently concave ; upper lip formed by a flatly curved 

 segment of the unthickened side wall and bearing a pair of strong 

 imperforate tubercles immediately adjoining the lower lip and in 

 obvious continuation of the bases of those spines which have formed 

 the front wall; above these tubercles the upper lip may bear, when 

 there is no ocecium, one or two or even occasionally three minor 

 tubercles; if there is an ocecium it starts immediately above the 

 principal tubercles, and the lip of the aperture is cut away below it. 



Ocecia rather large, globose on the whole but nearly straight-sided 

 in the lower part ; free edge slightly concave. 



1 Geol. Mag., 1910, p. 391, PI. XXX, Figs. 9, 10. 



