163 



M. centralis Mac Gillivr. 



A monograph of the tertiary Polyzoa of Victoria, Transact. Royal Soc. of Victoria, 



Vol. IV. 1895, pag. 55, PI. VIII, fig. 3. 



(PL VII, figs. 1 a-1 d). 



The zooecia which ax-e bounded by a rounded granular marginal ridge are large 

 (length 1.3 mm.), broad, hexagonal, thick- walled, very strongly arched and within 

 the brown covering membrane finely tuberculated and provided with small, 

 scattered pores. The aperture, which is situated at a shorter or longer distance from 

 the distal margin of the zooecium, is surrounded by a thick, wall-like peristom. 

 It is large, almost semi-elliptical, but with the lateral margins somewhat con- 

 verging proximally, where it is cut off straight. Within this proximal margin we 

 find in the whole breadth of the aperture a ridge-like, raised part supporting 

 the operculum, and within the distal margin of the aperture there is a strong 

 vestibular arch which is somewhat angularly bent from side to side. The two 

 proximal corners of the extremely thick, calcified, tuberculated operculum, covered 

 like the rest of the frontal surface by the covering-membrane (fig. 1 c), are se- 

 parated by an extremely small sinuation from the remaining part of the proximal 

 margin, and accordingly a very small slit appears on each side. In each of the 

 proximal corners is seen a small triangular-rounded hinge-tooth. Each distal 

 wall and the distal half of each lateral wall is provided with a long pore-chamber 

 (fig. 1 d), with a row of uniporous rosette plates. 



Avicularia of general structure are wanting on the fragment examined, on 

 which however was found a zooecium with an aperture of peculiar structure 

 fig. 1 b). It is more oblong than the others, and the two distally somewhat con- 

 verging lateral margins meet in a distal margin, which has a median sinus. In 

 this an almost black, short, feeler-like filament takes its origin from the covering 

 membrane, and some way further down there is a similai'^one issuing on each 

 side. These filaments quite correspond with those discovered by Harmer in Piiel- 

 lina radiata. The proximal margii^ of the aperture is furnished with a low, broad 

 denticle. 



Of this species I have had the opportunity of examining a small fragment 

 from Wanganui, which incrusts a shell-fragment, and which was sent to me by 

 Miss Jelly labelled ^Monoporella crassatina<i, under which name I have mentioned 

 it in » Studies on Bryozoa« ^). M. Clarkei Tenison-Woods belongs to this genus, 

 and in the figure Mac Gillivr ay- gives of this species we also see a zooecium 



' 56, p. 7. ' 76, p. 55. 



11* 



