ANTARCTIC BRYOZOA — ROGICK 295 



colony texture is rather smooth but has a faintly embossed surface 

 . where ovicells occur in rows or patches. The thickness of a bilaminate 

 blade is from 0.547 to 1.08 mm. (average 0.772 mm.). 



Zooecia: The zooecia are of four types, those with or without 

 ovicells and those with or without avicularia. Both some of the 

 ' ovicelled and some of the nono vicelled zoids have suboral avicularia ; 

 others lack them. The zooecia are 4- to 6-sided, longer than wide 

 and faintly outlined by their thin salient mural rims. The frontal 

 surface looks like a coarse woven mesh because it is perforated by nu- 

 merous, large, closely set pores and is also pebbled between the pores. 

 It is flattened to gently convex except in the peristome and avicularial 

 regions, which protrude or are elevated. The frontal wall is thicker 

 than the side and back walls. The side walls are perforated by about 

 six large pores. 



Avicularium: Only one type of avicularium, the suboral, is present. 

 It may be lacking in about half the zoids of some colonies. There is 

 never more than one per zoid. Wlien present, these broadly elliptical 

 to nearly rounded avicularia always occur in the same position and 

 orientation — in the midline, immediately below the peristomial sinus, 

 with the mandible pointing proximaUy. The area back of the cross 

 bar and mandible is very short and curved. The mandibular area 

 and mandible are a bit longer than a hemisphere. The avicularium 

 is elevated above the general frontal surface. The mandible is 

 parallel \vith the frontal surface but the back area may in some 

 instances slant downward, distally. The mandible has two converging 

 sclerites (pi. 27, E). 



Orifice: The orifice is at the extreme frontal-distal edge of the 

 zooecium. Its distal border is the wall of the next neighboring zoid. 

 The secondary orifice is bordered by a partial peristome. The pri- 

 mary orifice is deeper. The peristome is mostly frontal. It consists 

 of two more or less elevated and prolonged tabs or processes between 

 which is located the wide sinus or notch. The tabs are sometimes 

 parallel, sometimes almost meeting at the tips (pi. 27, C). As a result, 

 the sinus is sometimes fingerlike, sometimes nearly circular. The 

 peristome projects outward at an angle from the frontal surface, 

 like the spout of a pitcher. The secondary orifice is more or less 

 hemispherical distaUy and deeply sinuate proximall^, roughly re- 

 sembling the side view of a mushroom. The primary orifice is broadly 

 curved distally and provided with a wide low truncated lyrula and 

 two cardelles proximally. It is wider distally than proximally. The 

 chitinous operculum is rather thin and delicate. Two curved lateral 

 sclerites, one on each side, serve for muscle attachment (pi. 27, D). 



