NO. 2 OSBURN : EASTERN PACIFIC BRYOZOA — CHEILOSTOMATA 439 



scured with age. The primary aperture is about 0.11 to 0.13 mm wide 

 by 0.10 mm long, rounded, the proximal border straighter with a 

 moderately broad lyrula which has a lateral point at each corner. The 

 primary peristome is low and bears a series of 8 or 10 long, slender 

 vertical spines; the secondary peristome begins as an umbonate process 

 proximal to the aperture and develops into a tube of varying height 

 (occasionally as much as 0.40 mm), formed by the pleurocyst which 

 usually fuses with the spines and often carries a series of the areolar 

 tubules with it up on the sides. The tips of the spines may often be 

 seen projecting above the partially developed peristome. The fully de- 

 veloped peristome also usually bears a small proximal denticle projecting 

 inward from the tip of the tube. No avicularia. The dietellae are 

 small and numerous. 



The ovicell is semiglobular, smooth, imperforate, recumbent, resting 

 on the succeeding zooecium, the pleurocyst of which grows up over it, 

 carrying the small tubules with it; in complete calcification it appears, 

 like the frontal, to be covered by a tremocyst. 



Hincks described it from British Columbia, "probably the commonest 

 species amongst Dr. Dawson's dredgings." Canu and Bassler listed it 

 from the Pleistocene of Santa Monica, California, under the genus 

 Phylactella; in complete calcification there is much resemblance to that 

 genus, but the supposed frontal pores are merely the ends of the areolar 

 tubules distributed through the pleurocyst. Our abundant material 

 represents all stages of the development. O'Donoghue did not recognize 

 it, but I am of the opinion that his record of M. microstoma belongs 

 here, and that his M. simplicissima var. perjorata, "with scattered per- 

 forations" is the complete stage of development of the same species. 



Hancock Stations: taken at 10 stations about the islands of? southern 

 California; at Point San Eugenio and San Juanico Bay, Lower Cali- 

 fornia; at Clarion Island, west of Mexico; and at three stations, Charles, 

 Albemarle and James Islands, Galapagos. This temperature range is 

 very wide, but there are numerous other species with a similar range. 

 The known bathymetric range is from shallow water down to 135 fms. 



Genus HEMIGYCLOPORA Norman, 1894 



"Zooecia with pores confined to the sides and sometimes anterior 

 portion of the front wall. Mouth-opening well arched above, lower 

 margin straight (no denticle within the lip). Reproduction by ooecia, 

 which are imperforated. No avicularia." Norman. Genotype, Lepralia 

 polita Norman. 



