NO. 2 OSBURN: eastern pacific BRYOZOA — CHEILOSTOMATA 445 



5. Aperture rounded, its proximal border more or less sinuate, 



vestibular arch beaded Rhynchozoon 



Proximal border of aperture straight or broadly arcuate, 



vestibular arch slightly or not at all beaded . . . Lepraliella 



Genus RETEPORELLINA Harmer, 1933 



"Zoarium ramose, Reteporelliform, not fenestrate; or, if vi^ith anas- 

 tomoses, having many of the fenestrae long and slit-like. Frontal pores 

 seldom more than one pair, often inconspicuous or absent. Peristomes 

 frequently cylindrical or tubular, with marginal teeth or marginal denti- 

 cles ; sinuate or with a closed labial pore. Frontal avicularia various, a 

 strong bicuspid avicularium being characteristic but not always present. 

 Ovicells typically elongate and pyriform, wider distally, often with a 

 narrow, persistent, median fissure or groove, the small labellum distinct 

 but not carinate; lateral sinusus wanting; lateral flanges extending 

 proximally considerably beyond the labellum flanges" (Harmer 1926: 

 580). Genotype, Retepora denticulata Busk, 1884. 



The genus differs from Reteporella Busk, 1884 (the other non- 

 fenestrate genus), in which the ovicell is much shorter, with only a 

 vestigial labellum and no lateral flanges. 



Reteporellina bilabiata new species 



Plate 53, figs. 11-14 



Zoarium erect to a height of 20 mm, and branches in contact may 

 occasionally fuse, irregularly fan-shaped, branching dichotomous; width 

 of branch 1.00 mm or more. Zooecia in about 6 (4 to 8) alternating 

 series, elongate and tubular (averaging about 0.50 mm long by 0.26 

 mm wide), peristomes prominent and tubular in young zooecia, labial 

 pore soon enclosed and occluded. With further calcification a somewhat 

 triangular lip rises on each side of the secondary aperture, usually with 

 3 denticles on each lip ; the secondary aperture thus remains incomplete 

 on the proximal and distal borders; the secondary sinus (spiramen) is 

 deep and very irregular in form. The primary aperture is nearly straight 

 on the proximal border, about 0.11 mm wide by 0.09 mm long. The 

 frontal pores are more numerous than is usual in this genus, 2 at the 

 proximal end and 2 (1 to 3) on each side. 



Labial avicularia are entirely wanting. The frontal avicularia are 

 of two kinds: 1, a large form, usually in the midline with a pointed 

 rostrum more or less elevated and directed proximally (varying con- 



