230 ALLAN HANCOCK PACIFIC EXPEDITIONS . VOL. 6 



depressed throughout; wall distinctly and coarsely perforate, the early 

 biserial portion frequently with short costae giving a roughened appear- 

 ance; aperture narrowly elliptical, terminal. Length 0.40-0.45 mm.; 

 breadth 0.15-0.18 mm.; thickness 0.04-0.07 mm. 



Holotype (AHF no. 49) from Station 319. 



This species differs from B. zanzibarensis Cushman in the more com- 

 pressed test, very different ornamentation, and more elongate, slender 

 form. 



There is considerable variation in the early biserial portion of the 

 test which ranges from almost smooth to distinctly costate. 



Stations: 61, 62, 69, 215, 256, 313, 314, 316, 319, 321, 543, 558. 



Type locality. — Port Parker, Costa Rica, in 5 fms. 



Distribution. — In the Gulf of California, Mexico, in 10 to 110 fms.; 

 off Costa Rica in 5 to 14 fms.; off Panama in 12 to 25 fms.; and off Co- 

 lombia in 50 fms. 



