NO. 2 OSBURN : EASTERN PACIFIC BRYOZOA — CHEILOSTOMATA 443 



The ovicell is very large, broader than a zooecium, and the fertile 

 zooecium has a long transverse aperture that contrasts sharply with the 

 apertures of the ordinary zooecia. Triangular avicularia are often 

 present at the side of the aperture. 



Trigonopora pacifica new^ species 

 Plate 58, fig. 9 



Zoarium encrusting, covering large areas on shells; dark reddish 

 brown or purple, due to the pigmentation of the thick ectocyst which 

 covers the whole surface except the aperture and the avicularia. The 

 dorsal wall is thin and smooth. 



Zooecia moderately large, length 0.65 (0.50 to 0.75) mm, width 

 0.35 to 0.45 mm; quadrangular or somewhat ovate; little ventricose; 

 the whole surface to the edge of the peristome covered with a thick 

 smooth ectocyst, beneath which is the roughly granular pleuroc^^st per- 

 forated at the edges by a row of large areolar pores, which are separated 

 by short costae. The peristome is somewhat elevated, thin, rounded or 

 short-ovate, with a deep, narrow proximal sinus, but without the 

 "lyrula." The primary aperture is nearly circular, about 0.15 mm in 

 diameter, without a sinus but the peristomial sinus (rimule spiramen) 

 rises immediately above it. 



The avicularia, which are not abundant, are located at one or both 

 sides of the peristome, directed forward and inward and the tip of the 

 mandible curved outward slightly; the mandible is shorter and less 

 curved than in the Atlantic species (T. unguiculata Canu and Bassler 

 1928:128). 



The ovicell is remarkable for its size and structure, being noticeably 

 larger and wider than the zooecia, endozooecial and deeply embedded 

 but very conspicuous because of the size (0.75 mm wide by 0.60 mm 

 long) ; covered by the pigmented ectocyst, beneath which the ectooecial 

 wall is extremely rough and perforated by numerous small pores. The 

 ooecial aperture is a transverse slit 0.40 to 0.50 mm wide by about 0.13 

 mm long. The fertile zooecia are much modified, (gonozooecia), usually 

 much shorter than normal zooecia and distally widening to the breadth 

 of the ooccium ; the peristome is a raised lip the full width of the ooecium, 

 upon which it extends for a short distance. 



This species bears a close resemblance to T. unguiculata (Canu and 

 Bassler) from the Gulf of Mexico, but the measurements are much 

 smaller, the avicularia are shorter and located farther toward the distal 

 end and the ooecial cover is perforated by numerous small pores. 



