ANTARCTIC BRYOZOA — ROGICK 269 



Orifice: The primary orifice is gently arched distally. It is so 

 deeply set back of the mucros that its proximal border is completely 

 hidden from view. Nonovicelled zoids (lowest one in pi. 18, A) show 

 pores along the peristomie; ovicelled zooecia generally show none or 

 exceedingly few, but have the ovicell frontal projecting down into the 

 peristomial canal a bit. Dimensions of the primary orifice: length 

 0.173-0.230 mm. (average 0.192 mm.), width 0.302-0.331 mm. 

 (average 0.320 mm.). 



OvicELLs: An ovicell forms a low, scarcely recognizable mound 

 above the orifice. When observed from the inside the ovicells are 

 globular. Only two were measured: lengths 0.374 and 0.403 mm., 

 widths 0.346 and 0.374 mm. 



Types: Holotype, USNM 11243; paratypes, USNM 11244. 



Ecology: This species was dredged at Antarctic Station 104. Only 

 a few zoids of a cheilostome and a cyclostome (Bryozoa) and a cal- 

 careous worm tube grew on some colonies. 



Discussion 



The six species of the 1947-48 collection were extremely bothersome 

 because of the great sunilarity between them. They have the follow- 

 ing structures or characteristics in common: 



Thick channeled porous frontal wall. 



Thin back and side walls. 



Side wall has a few longitudinal rows of single pores along its frontal border 



and several multiporous rosette plates further in. 

 Two types of avicularia, one inside the zooecial cavity near the orifice, the other 



outside, also near the orifice. They are similar in appearance but differ in 



location and orientation. 

 End wall with a sieve plate and two calcareous processes. 

 Ovicell hyperstomial and immersed, diflBcult to see from the outside. 

 Presence of a frontal oral ledge which modifies the proximal border of the arched 



primary orifice. 

 Colony with nodes and internodes. 

 Triangular mandible in avicularia. 



The same six species of the 1947-48 collection differ on the following 

 specific points: 



Orientation of the internal avicularium. 



Orientation of the external avicularium. 



Number of external avicularia per zoid. 



Presence or absence of peristomial cap or visor. 



Orientation of the frontal oral ledge. 



General appearance of the colony or the growth form that it assumes. 



Number and location of the mucros. 



The internal avicularium is horizontal in position in C. nutti and 

 C. rossi. It is oblique in position in the other four new species. 



350640—56 



