331 



the larger or smaller (in the figure fairly small) basal wall of the vibracular 

 chamber. Through the basal surface of the distal half of each zooecium (fig. 4 c), 

 therefore, we can see 4 — 5 chambers and in rare cases only 3, in which case the 

 vibraculuni is wanting or does not reach to the basal surface. The basal surface 

 in the majority of the zooecia shows in its proximal half either a multiporous 

 rosette-plate or an opening. 



The ooecia, which have no pores, are sti'ongly arched and luberculated. 



The heterozooecia are developed as vibracula and occur singly on almost all 

 the zooecia in the colony. The large, projecting chamber, irregularly circular in 

 circumference, which is situated on one side of Ihe zooecium at a level with the 

 ascopore and with its longitudinal axis perpendicular to that of the zooecium, is 

 provided with a short mandible pointing outwards, which consists of a large, 

 oblique, triangular proximal part and a not much longer, dagger-shaped terminal 

 part (fig. 4 f). 



The colonies are free, two-layered, dichotomously branched and the single 

 branches, which are greatly widened at the end, have on each surface 8 — 45 rows 

 of zooecia. Similar bundles of radical fibres appear along the margins of the 

 colony as in the previous species; but on the other hand, radical fibres are want- 

 ing round the single zooecia. The basal wall of most zooecia is in the proximal 

 half provided either with a multiporous rosette-plate or with a corresponding 

 opening and in opposition to what is found in Mic. marginatu the zooecia in the 

 two layers of the colony correspond to each other. 



Of this species I have examined a colony from South Africa (Miss Jelly). 



Microporella flabelligera n. sp. 

 (PI. XXIII, figs. 6a-6c). 

 The zooecia edged oval, evenly arched, luberculated and provided with scat- 

 tered pores, which decrease in number outwards and which owing to the thick- 

 ness of the wall appear as canals in older zocrcia. The aperture which is sur- 

 rounded by 5, more rarely 6 spines dark at the base, the two outermost of which 

 are bifurcated, has a half-elliptical form, and its proximal, somewhat concave 

 margin grades over into the lateral margins on each side round a right-angled, 

 rounded corner. There is a distinct vestibular arch and a faintly developed 

 supporting beam. The operculum is strongly chitinized, dark-brown and pro- 

 vided on each side with a short muscular ridge, which runs out into a freely 

 projecting terminal part. The ascopore, which is of a considerable size and cir- 

 cular, has no inner protuberance and its margin may to a larger or smaller ex- 

 tent be provided with teeth-like projections. Immediately on the proximal side 



