297 



seem to be only a part of the avicularium. The case is however quite the same. 

 Nevertheless the genus Gepbyrophora may perhaps be preserved on account of its 

 possessing endozooecial ooecia. 



This family is nearly related to the Reteporidae, from which they differ by the 

 absence of spines, by a richer development of pores, by only possessing a weakly 

 developed vestibular arch as also by differences in the structure of the ooecia. It 

 is possible, however, that closer study of a larger number of forms of both fa- 

 milies will prove it difficult to define them sharply from one another. 



Synopsis of the genera. 



1) A tubular peristome provided with two or more avicularia and 

 with a suboral pore leading into the peristomial cavity: 



2) Hyperstomial ooecia Haswellia Busk. 



2) Endozooecial ooecia Gepbyrophora Busk. 



1) No peristome (hyperstomial ooecia): 



3) Avicularia without transverse bar; pore-chambers Myriozoella n. g. 



(Myr. crustaceum Smitt.) 

 3) Avicularia with transverse bar; no pore-chambers Myriozoum Donati. 



Haswellia australiensis Hasw. 



Haswellia australiensis Busk, Challenger, Zoology, Vol. X, Part I, p. 172, 



PI. XXIV, fig. 9. 

 Porina coronata var. labrosa Waters, Challenger, Zoology, Vol. XXXI, 



Part III. p. 32, PI. II, fig. 8. 

 (PL XVI, figs. 2 a-2 b). 



The zocecia elongated, narrow, without separating furrows, provided with nu- 

 merous pore-canals, the outer, oval openings of which are separated by arched 

 ridges and show a more or less distinct tendency to be arranged in longitudinal 

 rows. Whilst these openings in the younger parts of the colony are broader than 

 or as broad as the ridges, they decrease in extent as time goes on and finally 

 become quite closed. Each pore-canal ends inwardly in a uniporous rosette-plate 

 with a calcified outer area. The operculum is well-chitinized and its anter makes 

 the two-thirds of a circle. The accessorial part which is only separated from the 

 anter by a very small rounded sinus on each side is rather large, rounded trian- 

 gular and the lateral margins are a little concave. A very little indistinct muscu- 

 lar dot is placed on each side in the distal part of the operculum. The hinge-teeth 

 are well-developed. The fairly short, obliquely projecting oral tube, which posses- 

 ses only a small number of scattered pores, has an opening medially on its proxi- 



