482 R. M. Brydone — New Chalk Polyzoa. 



Avicidaria only of the type characteristic of the group, about 

 one-third the size of the zooecia, numerous, robust, and very prominent, 

 distributed irregularly, but with a strong tendency to succeed ocecia. 



This species occurs very sparingly in the zone of M. cor-angimium 

 in Hants and Kent and in the zone of 0. pihila in Sussex. Above 

 the latter zone the group is entirely unrepresented in my collection 

 until vre come to the Triminghanl Chalk. 



Membkanipora prjecipua, sp. nov. (PI. XXXV, Figs. 5-7.) 



Zoarium unilaminate, adherent. 



Zooecia large with fairly thick side walls overhanging very slightly ; 

 areas elliptical, average length from '65 mm. upwards, breadth from 

 •35 mm. upwards. 



Oaecia abundant but delicate, slightly globular, the free edge 

 coinciding with the outline of tlie area, the side wall of which is 

 exceedingly thin beneath them. 



Avicularia of two types — 



1. Interstitial, of the type characteristic of the group, nearly 

 as large as the zooecia and tending to introduce new rows of 

 zooecia; the hood is straight or even slightly concave in outline at 

 the upper end, and has a free edge embracing the upper half of the 

 aperture and then curving round and backwards to a point of 

 attachment on the outer margin ; there are distinct traces of a bar 

 across the aperture just below the hood. 



2. Vicarious, long drawn out and very gently curving, extreme 

 instances of the hour-glass type with traces of a bar across the lower 

 end ; they are the most graceful and delicate objects that I have met, 

 and the figures do not do them anything like justice. 



The vicarious avicularia are extremely capricious in occurrence ; 

 the interstitial ones are also rather capricious, but it is very rare 

 for any zoarium of decent size which suggests this species by the 

 dimensions of its zooecia not to show at least one recognizable, 

 even if damaged, avicularium of this type (Figs. 5, 7). 



This species, which is apparently confined to the Trimingham 

 Chalk, seems clearly a descendant or near relation of M. cucuUigera. 



Membeanipora sacerdotalis, sp. nov. (PI. XXXV, Figs. 8-10.) 



Zoarmm unilaminate, adherent. 



Zuceeia markedly pyriform with slender slightly overarching side 

 walls and narrowly elliptical areas of average length '5 mm. and 

 breadth -25 to '3 mm. ; in early stages the zooecia tend to be broadly 

 elliptical (Fig. 8). 



Ocecia very numerous but very delicate, long, and narrow, in ground 

 plan widest at the upper end and tapering gradually downwards, 

 markedly bottle-necked. 



Avicularia of two types — 



1. Interstitial, of the type characteristic of the group, small, long, 

 and narrow, with the hood very well developed and resembling 

 a monkish cowl, and a bar across the aperture sometimes preserved ; 

 the aperture almost invariably faces the centre of the zoarium, the 

 reversed specimens seen in Fig. 10 being quite abnormal. This 



