248 ME. A. W. WATERS ON 



lu many zooecia the central projection of the wall is fuuuel- 

 shaped, and this may be prolonged beyond the thick portion into 

 a delicate small transparent tube (fig. 13, tb.). When this was 

 first seen it was thought to be an accidental appearance, but 

 being found in other zooecia it is clearly normal. 



When the transA^erse wall forms a pouting projection (fig. 12), 

 then the tentacular sheath is attached to the lower part of the 

 projection (fig. 12, ts.), and there is a similar thin membrane, 

 like the tentacular sheath, arising from the point of junction of 

 the thick transverse wall with the zooecial wall, and this again is 

 attached lower down to the tentacular sheath (see figs. 12, 14, tb.y. 

 There is living tissue both below and above the transverse wall, 

 and the structure is seen to be in the main similar to what I 

 described as the closures of Seteropora claviforonis *, Waters,, 

 but the transverse walls and the calcareous closures are not 

 identical, though related. 



The diaphragm closing the tentacular sheath is near to the 

 above-mentioned transverse wall (fig. 14, dp.), and this last i& 

 not close to the calcareous closure, the distance apart usually 

 being about twice the diameter of the zocecial tube. There are 

 12 tentacles ; but no ovaria were seen in the specimen, while 

 there are a few young testes. 



Although I do not find as thick a wall in any other species of 

 Cyclostomata examined, yet there is a membrane ; and in Hornera 

 lichenoides, Pont., from the Arctic, it is sometimes fairly thick,, 

 and there is beyond the wall a conical projection lined with 

 large cells. In Diastopora ohelia, Johnst., there is a transverse 

 membrane, and the structure is somewhat similar in Lichenopora. 

 Having obtained the key, we may hope shortly to understand the 

 mechanism more thoroughly, and possibly the study of this 

 structure may throw much light upon Palaeozoic and other fossil 

 Bryozoa in which the tabulae are common. 



This thick wall stains much more deeply than the other tissues, 

 showing that it is not usually chitinous. 



Hah. Yictoria (MacGill.) ; Bass's Straits, 38 fath. {Bush). 

 Cape Horn Expedition : Station 170, Canal Pranklin, 95 metres, 

 + 7°-0 Cent.; Station 183, "10 milles au S.E. de la Posse 

 Sloggett," 816 met., +4°-9 Cent. 



* " Bryozoa, ' Expedition Antarctique Beige, 1904, p. 98, pi. 7- fig. 8. 



