NO. 2 OSBURN: eastern pacific BRYOZOA CHEILOSTOMATA 345 



slightly backward, and proximal to these is a deep and broad sinus or 

 poster, the whole aperture having a "key-hole" form. There is a well 

 developed vestibular arch which is sometimes faintly beaded. The peri- 

 stome is low, in older zooecia submerged below the level of the surround- 

 ing frontal crust. The operculum has the form of the aperture, with a 

 complete sclerite extending around from one cardelle to the other at 

 a distance from the border. Pointed avicularia are present, usually on 

 one or both sides opposite the aperture, but often wanting. Dietellae. 



The ovicell is hyperstomial, imperforate, not closed by the operculum ; 

 prominent when young, with longitudinal striae ; later with a semi- 

 circular area above the orifice, but the whole ovicell becomes embedded in 

 the thick frontal wall of the distal zooecium and completely buried within 

 it when calcification is complete. 



There is much variation in the size of the zooecia, those near the 

 center of the zoarium being much smaller than the outer ones. Typically 

 the avicularia are located near one or both sides of the aperture and 

 directed forward and laterally, but they may have any position on the 

 frontal and be turned in any direction, all on the same colony. Descrip- 

 tions and illustrations of this species do not indicate any areolar pores, 

 but calcined specimens always show a few. In complete calcification there 

 is often a small rounded umbonate swelling near the aperture. The 

 synonymity of cleidostomata Smitt with porcellana Busk has been dis- 

 puted, but Norman (1909:305) examined Busk's type in the British 

 Museum and states that "it proves to be a somewhat overgrown speci- 

 men of Smitt's L. cleidostomata." After observing the wide variation in 

 the supposed diagnostic characters of numerous Atlantic and Pacific 

 specimens I am unable to separate them. 



It is a warm water species, recorded from the Mediterranean Sea 

 and the Madeira Islands ; on the Atlantic coast from Florida to Santos 

 Bay, Brazil; and on the Pacific coast from the Galapagos Islands and 

 Peru northward to southern California. 



Hancock Stations. An abundant species, occurring at 66 stations. 

 The most southerly record is for Callao, Peru, and the northerly for 

 Santa Cruz Island off southern California; coastwise it was taken also 

 in Ecuador, Panama, Costa Rica and Mexico at various places, and off 

 shore at the Galapagos, Socorro and Clarion Islands. 



