B. M. Brydone — Chalk Polyzoa. 7 



III. — Notes on neav or imperfectly known Chalk Polyzoa. 



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



(Continued from Decade V, Vol. VIII, p. 156, 1911.) 



(PLATE I.) 



DiSCOFLTJSTRELLARIA TrIMENSIS, Sp. nOV. (PI. I, FigS. 1-3.) 



Zoarium small, highlj^ conical, slightly compressed in one direction, 

 very fragile. 



Zocecia rather bluntlj^ hexagonal, subradially arranged in straight 

 rows which from time to time diverge to admit a new row, length 

 •35-"4mm., width about the same; the area varies from distinctly 

 elliptical to practically circular; maximum length 'SS mm., breadth 

 •3 mm. 



Ooecia apparently not uncommon, though delicate and rarely well 

 preserved; they are strongly inflated, but nearly rectangular in plan, 

 with tlie free edge straight (when perfect) ; they roof in the upper 

 end of the zooecia, which is of abnormal length, and remain conspicuous 

 by their length when the ooecia have been destroyed ; they tend 

 to encroach slightly on the area of the succeeding zooecium. 



Avicularia of the hour-glass type, closely resembling those of 

 Memhranipora anguiformis {ante, April, 1910), but with the upper 

 part of the hour-glass larger than the lower and with indications of 

 a slender bar crossing the lower end of the neck of the hour-glass 

 similar to those shown by Memhranipora sagiUaria {ante, April, 1910). 

 They seem to be confined to the beginning of new rows of zooecia. 



The species occurs very rarely at Trimingham, and but for the 

 single specimen shown in Pig. 1, which is perfectly discoidal, though 

 as a cone it has lost its apex, I should not have ventured to publish 

 the opinion I had formed from fragments that it was a Discoflustrellaria. 

 The species is easily distinguishable by its avicularia (the ' cellules 

 avortees ' of the generic diagnosis). 



Laterofltjstrellaria robusta, sp. nov. (PI. I, Figs. 4-10.) 

 Zoarium strong, typically conical, but varying in height from 

 3 to 5 mm. ; the liigh specimens are genei'ally rather elliptical, the 

 low ones are generally circiilar. 



Zomcia symmetrically hexagonal ; the initial (and central) zooecium 

 is quite abnormal, being larger than the others and shaped like an 

 elliptical funnel, at the bottom of which is a long and narrow 

 triangular aperture with a stout and blunt projection from each side ; 

 over the base of the triangle and hiding the greater part of it there 

 liangs a sliort, broad, rounded projection at a level a little below the 

 rim of the funnel ; round the initial zooecium there is a ring of zooecia 

 of appi'oximateljr normal size and shape, but retaining modifications 

 of the stout internal projection of the initial zooecium, which often 

 simulate a front wall of ordinary Escharine type ; outside this ring 

 the zocecia (except for the first one or two of a row, which maybe sub- 

 triangular) are all alike, appearing on the surface as a regular network 

 of large, very slightly elliptical apertures with thin boundary walls, 

 divided from one another by fine sutures, and curving downwards 



