426 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 14 



8. Avicularium large and prominent townsendi 



Avicularium very small, conforming to the margin of the peri- 

 stome cellata 



9. Numerous giant frontal avicularia fortissima 



Frontal avicularia, when present, smaller; a high pointed umbo 



with costal ridges costata 



Rhamphostomella costata Lorenz, 1886 

 Plate SO, fig. 7 



Rhamphostomella costata Lorenz, 1886 :12. 

 Rhamphostomella costata, Nordgaard, 1906:30. 

 Rhamphostomella costata, Os\inm, 1912:244; 1919:610. 

 Rhamphostomella costata, O'Donoghuc, 1923:44; 1926:72. 



Encrusting, usually on stems and rising into flabellate bilaminate 

 expansions or contorted folds. The zooecia are large, 0.60 to 0.90 mm 

 long by 0.40 to 0.50 mm wide; distinct, the frontal arched and rising 

 into a high pointed umbonate process on the top of the avicularian 

 chamber which covers practically all of the width of the front; there 

 is a row of large areolar pores, between which strong costal bars run 

 up even to the tip of the umbonate process. This process is higher than 

 in the other species of the genus, a little asymmetrical in position, and 

 its tip is often developed into a transverse bar (variety cristata Hincks). 

 The primary aperture is round distally, the proximal border somewhat 

 straighter and a little asymmetrical, without cardelles, but with a small 

 lyrula which is often wanting. The secondary aperture is usually a 

 little angulated proximally, due to the overhanging base of the umbonate 

 process. A moderately large avicularium, with a subspatulate mandible 

 is located at the side of the base of the process and directed vertically. 

 Frontal avicularia with a triangular mandible are found on most of 

 the zoaria, located near the proximal end of the zooecia. 



The ovicell is large, about 0.40 mm wide, prominent, perforated 

 with large pores, more or less submerged by advanced calcification. 



A common arctic and northern species, extending down the Atlantic 

 coast to Cape Cod, Massachusetts, and on the Pacific coast to Puget 

 Sound. Recorded by O'Donoghue from a number of British Columbia 

 localities. 



Point Barrow, Alaska, down to 23 fms, G. E. MacGinitie, collector 

 (Arctic Research Laboratory). Also from Friday Harbor, San Juan 

 Island, Puget Sound, Dr. J. L. Mohr, collector. 



