198 U. M. Brydone — Chalk Folyzoa. 



areal outline, to be long and parallel sided with pointed ends ; at 

 the head the side wall has a slight but definite thickness ; the infold 

 of the side wall has a concave edge, which never quite hides the edge 

 of the front wall, and it can be clearly seen that these edges unite 

 in the projecting point ; the lower end of the avicularium is (in 

 correspondence with the zooecia) simple, not subpyriform ; the upper 

 and lower sections of the area are appi'oxiiuately of equal size. 



The basal lamina is distinctive and apparently so constant in 

 form as to be reliable for purposes of diagnosis, and I have figured 

 a small piece. 



This species is well distributed in the (restricted) zone of 

 A. quadratus in Hants, and is abundant in Sparks' Pit, near Cosham. 



Membranipoea cervicornis, sp. nov. PI, VII, Figs. 3, 4. 



This species, which succeeds M. Sparksi very closely in tiole, is 

 naturally very closely related to it, and is perhaps best described by 

 enumerating the points in which it differs from that species. It is 

 always adherent ; the zooecia have rounded side walls and no internal 

 front wall ; the avicularia and their areas tend to be short, broad, 

 and round-ended, the front wall is very wide, the upper section of 

 the area is smaller than the lower, and the constricting prominences 

 stand up very strongly and have flowing outlines suggestive of those 

 of a deer's antlers; no traces of ooecia have yet been observed. 



This species occurs sparingly in the base of the zone of ^. mucronata 

 at Portvsdown. 



Membeanipora plicatella, sp. nov. PI. VII, Fig. 9. 



Zoarhim unilaminate, free or adlierent, the free specimens showing 

 a strong tendency to tubular branching shapes, as if they had 

 incrusted seaweeds. 



Zooecia elongated, roughly hexagonal, with a considerable amount 

 of internal front wall at the foot and bounded by definite sutures ; 

 areas of very variable size, but relatively small, roughly oblong, with 

 gently convex sides. 



Ooecia not yet observed. 



Avicularia relatively very large, of general Lestietiri-type ; there 

 is practically no distinction between front wall and side wall at the 

 head, the two combining into a bowl-shaped ending ; the edge of the 

 infold of the side «'all seems to split into an upper and a lower 

 lamina, the upper one being cut back very early and dying out ; 

 the area is relatively very small, being little lai'ger than that of 

 the larger zooecia, and narrowly elliptical, and tlie constricting 

 prominences, which practically do not impinge on it, are median 

 in position. 



This species is fairly abundant at Triminghara. 



Membeanipoea ^dificata, sp. nov. PI. VII, Figs. 10, 11. 



Zoaritim unilaminate, always adherent. 



Zooecia long and narrow, with flowing outlines and separated by 

 faint sutures ; areas very variable in size but relatively very small 

 and situate quite in the upper half of the zooecia, wide and flatly 



