300 PROCEEDINGS OF THE NATIONAL MUSEUM vol. los 



delles generally, but variations occur even in the same colony as regards 

 the prominence and width of the lyrula and the presence or absence(?) 

 (at least the visibility) of the cardelles. The cardelles are two small 

 blunt pegs placed some distance from the lyrula, at the lower corners 

 of the orifice. However, it is not possible to see them in all orifices. 

 Whether they are absent or just directed inward, out of sight, could 

 not be determined without damaging the colonies. 



The opercidura is considerably wider than long. Its distal arch is 

 broad and low, being much wider than the proximal border, which is 

 drawn out into two chitinized points from which a reinforced edge 

 continues dis tally. 



Ovicell: Numerous ovicells are present. Young ones are gently 

 salient, globose, and provided with a membrane-plugged central pore, 

 while older ones are practically level with the frontal surface of the 

 next distal zoid. Their surfaces are gently beaded or granidar. 

 Nearly half of the ovicells have a single small oval frontal pore, vari- 

 ously placed — sometimes centrally, sometimes more distally or lat- ■ 

 erally. A few ovicells in the same colony may have an occasional 1 

 extra, smaller, irregularly placed pore. The remaining ovicells in a 

 colony may lack the central pore because advancing calcification has : 

 obliterated it. Some of the ovicells are bordered by a few large pores : 

 that are a part of the frontal surface of the surrounding or next distal I 

 zoid. In summary, the commonest ovicell frontal condition in a well 1 

 calcified colony is either solid or punctured by a single pore. In old i 

 colonies there is a fusion of the frontal layer of the ovicell with the 

 frontal of the next zoid, so there is no outward sign of demarkation i 

 between the two except that the zooecial frontal is uniformly porous ; 

 whUe that of the ovicell is not. .: j 



In a young colony of only about 50 zoids, growing on the back of a r' 

 Phylactella lyrulata colony from Station 226, ovicells ah-eady had made 

 their appearance, indicating that early sexual reproduction occurs in 

 this species. This colony also had a zoid with two peristomial spines. 



Distribution and ecology: A few small colonies were taken from 

 Stations 104, 184, 226, 240 and Rock 6 (station unknown). They 

 grew on various substrates: stones or pebbles as Rock 6 and Stations 

 184, 226, 240; Alcyonaria spicules at Station 226; other Bryozoa at 

 Station 104, and Phylactella lyrulata at Station 226. 



Affinities: It is with some hesitation that these Antarctic spec- 

 imens are assigned to the same species as MacGillivray's Australian 

 fossil species {S. ordinata) originally described from Schnapper Point, 

 Muddy Creek, and Moorabool deposits whose age is variously given 

 as Eocene, Oligocene, or early Miocene (MacGillivray, 1895, p. 2). 

 Following is an abridged version of MacGUHvray's (p. 93) description of 

 S. ordinata: "Zooecia . . . separated laterally by deep furrows . . . 



