ANTARCTIC BRYOZOA — ROGICK 247 



I Zooecia: Zooecia are heavily calcified, especially around the edge 

 )r mural rim. Some are pentagonal, others hexagonal, and are ar- 

 •anged horizontally about the stem in a series of 10 or 11 zoids (pi. 

 i),M). In younger or less heavily calcified zooecia the mural rim 

 s gently raised (pi. 9,H) but in most zooecia the calcification process is 

 so advanced that the zooecial boundaries are depressed grooves (pis. 

 },G,M; 10,A) and the frontal surfaces are slanted downward toward the 

 aiural rim. Zooecial length varies from 0.584 to 0.869 mm. (average 

 3.692 mm.) and width from 0.490 to 0.585 mm. (average 0.542 mm.). 

 Raised cryptocyst ridges, somewhat beaded in spots, are present in 

 some very old zoids (pis. 9,G; 10,A). Also, delicate, gently cm-ved 

 parentheses lines are present near each side of the aperture (pi. 9,G). 

 rhey are thin yellow lines which do not meet at the top or bottom. 

 In some zooecia and avicularia the cryptocyst may be faintly tubercu- 

 late. 



■ Orifice: The zooecial orifice is a longer-than-wide truncate oval 

 with two strong teeth placed at or near its two proximal corners 

 (pi. 10,A). It is placed in a slightly depressed frontal area some dis- 

 tance away from the distal edge of the zooecium. The condyles or 

 teeth articulate with the oval transparent areas on the operculum 

 (pl. 9,G). 



Operculum: The operculum has the shape of the orifice (pl. 9,G). 

 Its length varies from 0.202 to 0.230 mm. (average 0.215 mm.) and its 

 width from 0.130 to 0.158 mm. (average 0.149 mm.). The curved 

 rim is chi tin-reinforced. The proximal boundary is hard to distin- 

 guish. A sclerite extends from the outer border of each of the two 

 oval transparent articular areas into which the orifice teeth fit. 



Ovicells: No ovicells were seen in the sample. Livingstone (1928, 

 p. 39) stated that they were endotoichal. 



Avicularia: The avicularia are vicarious, replacing a zooecium 

 in the horizontal series (pl. 9,M). Their shape varies from a diamond 

 to an elongated pentagon (pl. 9,J-L), and their size is comparable to 

 that of the zooecia. Avicularian length ranges from 0.664 to 0.837 

 mm. (average 0.774 mm.) and width from 0.316 to 0.411 mm. (average 

 0.363 mm.). The tip of the acutely triangular pointed beak is raised 

 frontally (pl. 9,K,M). The opesia has a median proximal sinus 

 bordered on each side by a ledge (pl. 9,J,K) with which the mandible 

 articulates. 



Mandible: The falciform mandible is sharply pointed, triangular 

 in outline, with the distal tip curved inward (pl. 9,F,I,J). A pro- 

 nounced keel and other chitinous reinforcements near the base, as weU 

 as the median peg which fits into the opesial notch, are characteristic 

 of the mandible. The mandible is large, measuring from 0.403 to 

 0.461 mm. (average 0.437 mm.) in length and from 0.187 to 0.246 mm. 

 (average 0.208 mm.) in width. 



