NO. 2 OSBURN: eastern pacific BRYOZOA — CHEILOSTOMATA 455 



2. A tall pointed or cylindrical process proximal to the aperture . . 3 

 No tall processes present 4 



3. An uncinate process in the aperture at the base of the oral avicu- 



larium, oral sinus indistinct bispinosum 



Uncinate process wanting, oral sinus distinct, suboral erect proc- 

 esses usually very numerous spicatum 



4. Zooecia large, 0.65 to 0.80 mm long, oral avicularian process 



broad and long, projecting far over the aperture . . grandicella 

 Zooecia smaller, avicularian process not unusually large ... 5 



5. Aperture with a distinct schizoporellidan sinus, the frontal costate 



to the base of the avicularium tumulosum 



Sinus broader and shallower, the frontal weakly costate around 

 the border rostratum 



Rhynchozoon bispinosum (Johnston), 1849 

 Plate 55, figs. 6-7 and Plate 54, fig. 9 



Lepralia bispinosa Johnston, 1849 :326. 

 Rhynchopora bispinosa, Hincks, 1880:385. 

 Rhynchozoon bispinosum, Hincks, 1895. 

 Rhynchopora bispinosa, O'Donoghue, 1923 :47. 

 Rhynchozoon bispinosa, O'Donoghue, 1926:73. 



Zoarium encrusting shells. Marginal zooecia quite regularly arranged 

 in quincunx, moderate in size (length 0.45 to 0.60 mm, width 0.30 to 

 0.40 mm), the frontal much inflated, smooth with never more than a 

 trace of costal ridges, 6 or 7 areolar pores on each side. The primary 

 aperture is subcircular, a little broader than long (0.14 by 0.12 mm) 

 with a broad and very shallow sinus ; the vestibular arch slightly beaded. 

 The suboral avicularian chamber is a bulbous, moderate swelling at 

 one side of the midline and projecting forward over one side of the 

 aperture; the mandible small (usually about 0.10 mm long) and 

 directed laterally; only a trace of an uncinate process at the base of 

 the chamber. In secondary calcification the front becomes very thick 

 and corrugated but not regularly costate; the secondary aperture some- 

 what ovate with a rounded notch or sinus between the base of the avicu- 

 larium and a slight prominence opposite it. The primary aperture is 

 obscured by the overhanging walls of the frontal and the avicularian 

 chamber. Frontal avicularia rare, similar in size but with a more acute 

 mandible, usually on a somewhat elevated chamber. Spines 2, widely 

 separated, found only on marginal zooecia and soon lost. 



