NO. 2 OSBURN: eastern pacific BRYOZOA CHEILOSTOMATA 347 



is a moderately broad and deep sinus or poster, semicircular in form. 

 The vestibular arch is well developed and beaded. The primary peristome 

 is low and smooth, but the frontal forms a secondary peristome which 

 is irregularly thickened and often mucronate or umbonate on the proximal 

 border in full calcification ; 4 to 6 oral spines are usually present. Avicu- 

 laria are numerous and various, ovate to spatulate or pointed in form, 

 oral or frontal, immersed or mounted on mamillate processes, the aper- 

 ture beaded like the oral margin. Dietellae are present. 



The ooecia at first are prominent, embedded only in full calcification ; 

 with a large semicircular and lightly striated area above the orifice which 

 is not covered by the secondary calcification ; the wall eventually becomes 

 very thick and irregular. 



In secondary calcification this species varies greatly, but the primary 

 characters are quite constant, except for the form and position of the 

 avicularia. The zooecia near the middle of the colony are much smaller 

 than the later ones, graduated from about 0.30 to 0.60 mm in length, 

 and the ovicell also varies from 0.15 to 0.18 mm in width. 



The reasons for transferring this species to the genus Hippoporina 

 have been given by Osburn (1940:429), the nature of the frontal, the 

 form of the aperture, the structure of the operculum, the arrangement 

 of the avicularia, and the nature of the ovicell. 



The species was described from Madeira. It is an abundant form on 

 the Atlantic coast from Cape Cod, Massachusetts to the Bay of Santos, 

 Brazil. Recorded also on the Pacific coast from Gorgona, Colombia, 

 and from the Galapagos Islands by Hastings. 



Hancock Stations: Taken at 62 stations from Ecuador to the Gulf 

 of California, abundant about the Galapagos Islands and Clarion Island. 



Hippoporina ampla new species 

 Plate 41, figs. 6-8 



The zoarium is encrusting on shells and corallines, white and glisten- 

 ing. The zooecia are large, 0.90 mm long (0.70 to 1.10) by 0.80 mm 

 wide (0.65 to 0.95), very distinct with deep grooves even in complete 

 calcification, somewhat hexagonal in form. The frontal is a granular 

 pleurocyst with 2 or 3 rows of pores and a large central imperforate area ; 

 in advanced calcification some of the granules on the proximal area 

 become elevated into short, erect, pointed processes. The aperture is 

 more or less removed from the distal border, pyriform, with sharp 

 cardelles directed backward, and proximal to these is a moderately broad 

 poster; 0.18 to 0.20 mm long by about 0.16 mm wide, the poster 0.10 



