ANTARCTIC BRYOZOA — ROGICK 235 



0.805 mm.) long and 0.230 to 0.389 mm. (average 0.333 mm.) wide. 

 They may occur singly or in 2's or 3's on a stalk in the same series. 

 Their raised siibtriangular beaks point distally and are raised 

 in the form of an inverted V at the distal half or third of the 

 avicularium (r in pi. 4, A). The greater part of the avicularial 

 opening or opesia is covered by a triangular mandible. The dimen- 

 sions of this triangular space are: length from 0.374 to 0.418 mm. 

 (average 0.389 mm.); width 0.130 to 0.173 mm. (average 0.154 mm.). 

 This triangular space is set off from the lower sunken hemispherical 

 proximal opening by the two conspicuous ledge-like condyles (pi. 4, A, 

 and L in pi. 4,B) on which the mandible articulates. This proximal 

 hemispherical part is called the "area" in Canu and Bassler's works 

 (1920, p. 62) and is depressed in Cellaria vitrimuralis. 



The elongate, subtriangular mandible is directed distally. Its 

 dimensions, based on only three readings, are: length from 0.158 to 

 0.346 mm. (average 0.300 mm.); width 0.202 to 0.216 mm. (average 

 0.206 mm.). Its edge is chitin-reinforced. There is a thinner, more 

 transparent large central area in the mandible. From the basal 

 corners of the mandible two converging chitinous bars or sclerites 

 (s in pi. 4,B) encroach upon this central area. There is a prominent 

 sharp tooth or spike turned inward from the mandible apex (pi. 4,G). 

 From the center of the basal bar, which marks the broad end of the 

 mandible, projects inward a small curved process. Two bundles of 

 muscle fibers attach above this basal median process, one on each side 

 (pi. 4,A, and u in pi. 4,B). 



The avicularia take the place of the regular zoids in a series (pi. 

 4,H). 



Kadicles: Extremely thin-walled, transparent, pale yellow tubules 

 exit through the frontal wall of some of the zoids (pi. 4,1). These 

 radicles are often quite long. Their diameters increase until they 

 become one-half to three-fourths the diameter of the zooecial branches. 

 They are directed proximally. Jomts or nodes are more deeply 

 colored (deep yellow to amber) than are the frontal radicles (pi. 

 5,E). The nodes seem to be part of the inner zooecial wall and are 

 straight. No tangle of radicle fibers occurs at the joints between 

 branches in this species. 



Types: Holotype, USNM 11213; paratypes, USNM 11214. 



Ecology: The branches of Cellaria vitrimuralis were generally 

 free of overgrowing organisms, but occasionally Foraminifera, cyclo- 

 stomatous Bryozoa and Hippothoa would be found attached to them. 

 Cellaria vitrimuralis was collected at Antarctic Station 104. The 

 amount of material available for study was a very small jar which 

 contained numerous colony fragments. 



