BRYOZOA OF THE PACIFIC COAST 

 OF AMERICA 



Part II, Cheilostomata-Ascophora 



By Raymond C. Osburn, Ph.D., D.Sc. 



Plates 30-64 



A report based chiefly on the Bryozoa collected by the Allan Hancock 

 Expeditions, 1933-1942, in the Velero III. (See pages 1-2 of Part I.) 



ASCOPHORA 



Levinsen (1909:213) defined the "Suborder Ascophora" chiefly on 

 the presence of a compensation sac or ascus, which suggested the name. 



It may appear somewhat illogical to apply the term "suborder" while 

 there is still difference of opinion as to where the Anasca leave off and 

 the Ascophora begin. However, with the exception of the Cribrimorpha 

 and a few other scattering genera there is no doubt as to their position 

 for the differences are very distinct. This does not appear a proper place 

 to enter into an extended discussion of the origin and evolution of the 

 Ascophora and, since the subdivision is a very convenient one, I shall 

 continue to use it in the hope that future research will clarify our knowl- 

 edge of the relationships. 



Suborder AsCOPHORA Levinsen, 1909 



The frontal area is completely calcified, with the exception of the 

 aperture, and beneath this is the compensatorium or compensation sac 

 which is a hydrostatic arrangement permitting the influx and outflow 

 of water when the polypide is extruded or withdrawn. As a rule this 

 sac opens into the proximal part of the aperture, but in some cases there 

 is a separate opening, the ascopore, situated proximally to the aperture. 

 The operculum is usually compound, hinged on the sides, the larger 

 distal portion opening upward to permit the extrusion of the tentacles 

 while the small proximal part is deflected downward to open the com- 

 pensation sac. When an ascopore is present the operculum is simple, 

 lacking the proximal part. 



[271] 



