338 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 14 



Gemelliporidra colombiensis new species 



Plate 40, figs. 11-12 



Zoarium encrusting small shell fragments, the surface rough, pale 

 yellow. Zooecia small, 0.35 to 0.45 mm long by 0.25 to 0.30 mm wide, 

 distinct only when young. The frontal is a tremocyst with small pores, 

 thick, and so rough that the pores are difficult to see except when cal- 

 cined. The aperture is longer than wide, 0.10 mm long by 0.08 mm 

 wide, slightly pyriform, the small cardelles set well back and the poster 

 forms a broad arc between them. The operculum is moderately chitinized, 

 light yellow, a narrow sclerite extends around from one cardelle to the 

 other slightly within the margin. The peristome is low, thin, smooth 

 and without spines; the secondary peristome, formed by the thickening 

 of the frontal wall, does not occlude the aperture. A comparatively 

 large avicularium is situated on one side proximal to the aperture, the 

 rostrum tilted upward at an angle of about 45°, the mandible semi- 

 elliptical and directed laterally, frequently wanting. 



The ovicell is comparatively large, 0.18 to 0.20 mm wide, globular 

 and very prominent, not closed by the operculum, perforated like the 

 frontal but the surface less coarsely granulated ; a small umbonate 

 process sometimes present directed backward over the aperture. The 

 ovicells are present in such numbers that the surface is obscured over 

 much of the zoarium. 



The nature of the aperture and operculum, the ovicell and the frontal 

 avicularium appear to ally this species with Gemelliporidra, but it is 

 much smaller and neater in appearance than others of this genus. 



Type, AHF no. 67. 



Type locality, Colombia, a single colony in the Hancock Collections 

 without further data. Also Hancock Stations 277, Tiburon Island, 

 Gulf of California and 539-36, Angeles Bay, east coast of Lower Cali- 

 fornia, at 1 to 16 fms. 



Genus HIPPODIPLOSIA Canu, 1916 



Frontal a tremocyst with numerous large pores which become in- 

 fundibulate, the tremocyst does not reach the proximal border of the 

 aperture and leaves a small, smooth area. The aperture is rounded with 

 a broadly arcuate or somewhat sinuated proximal border. The ovicell 

 is perforated, somewhat depressed on the front and marginated. Avicu- 

 laria sometimes present. Genotype, Hippodiplosia verrucosa Canu, 1916. 



