R. M. Brydone — New Ghalk Polyzoa. 99 



indicated in a few zooecia at tlie top of Fig. 5, from which the 

 ocecia have been broken away. 



The species is fairly regular in occurrence in the zone of 

 If. cor-testudinariiim at Seaford. It is fairly intermediate between 

 the published figures of Flustrina constficta, D'Orb.,^ and F. ovalis, 

 D'Orb.,^but Canu in his " Kevision " throws doubt upon the validity 

 of either of these species. 



Membkanipoka mxtltifissa, sp. nov. (PI. VI, Figs. 7, 8.) 



Zoarhim unilaraiuate, incrusting. 



Zooecia of medium size, average length "5 to "6 mm., breadth '4 mm., 

 without any definitely visible interzooecial sutures; apertures 

 broadly oval, flattened at the anterior end, enclosed by rather lounded 

 margins which approach one another rather closely laterally but are 

 quite distant longitudinally; a pair of rather large sub-tubular pores 

 occur very regularly on the outer edges of the margins just beside 

 the anterior end of the aperture, while between the margins there 

 are numerous irregularly scattered and less pronounced openings, 

 some of which are tubular, while others are mere fissures possibly 

 along zooecial boundaries. 



Ocecia fairly abundant, always broken, semicircular in ground plan. 



Avicularia probably of two kinds — {a) accessory, represented by 

 the paired marginal pores, (h) vicarious, scarce, of hour-glass type, 

 with a long area of constriction, traces of a cross-bar at its lower end, 

 a narrow internal front wall in the short round anterior lobe, and no 

 internal front wall in the small posterior lobe, which has a very 

 slender rim marked off by a little furrow, a feature not brought out 

 by the photographs. 



This species occurs in the zone oi M. cor-anguinum at Gravesend. 

 The relative size of its paired pores, no less than its possession of 

 vicarious avicularia, distinguish it from any figured species, except 

 M. dolium, Bryd. 



Membeanipoea Sevingtonensis, sp. nov. (PI. VI, Fig. 9.) 



Zoarium unilaraiuate, free. 



Zooecia large, average length "7 mm., with oval apertures narrowing 

 considerably to the anterior end, which is flattened by the edge of an 

 inward sloping shelf, and surrounded by raised margins almost in 

 contact with one another and bearing from seven to nine pairs of blunt 

 imperforate denticles, of which those round the anterior end are very 

 slender : at the foot of nearly every zooecium there is a large, more 

 or less semicircular, hollow thin-walled protuberance, which is 

 probably avicularian; between this and the aperture the raised 

 margin dies away and the tubercles disappear ; there are no other 

 indications of avicularia. 



Ocecia occurring erratically, shortly and widely conical with 

 rounded ends and a free edge apparently almost straight; when they 

 are present that part of the apertural margin which they embrace 

 does not undergo any depression, but is bare of tubercles ; they may 

 push to one side the protuberances of the succeeding zooecia or cause 

 them to be absent. 



1 Pal. Cr^t. Franc?., vol. v, p. 304, pi. 702, figs. 5-7. 



2 Loc. cit., p. 304, pi. 702, figs. 8-10. 



