FORAMINIFEKA OF THE NORTH PACIFIC OCEAN. 73 



Distribution. — This species is typical of tropical coral reefs in 

 shallow water. Brady under the stations listed in the Chal- 

 lenger report gives its occurrence at one North Pacific station, 260A, 

 in 40 fathoms from the Honolulu coral reefs, Hawaiian Islands. 

 Bagg records it from the same islands in deeper water, Albatross 

 D4174 in 735-865 fathoms, and H4568 in 1,274 fathoms. Rhumbler 

 records it from shallow water or shore sands of Laysan Island. I 

 have had specimens from several Nero stations in the vicinity of the 

 Hawaiian Islands ranging in depth from 21 to 271 fathoms; also 

 specimens were found in shore sand from Midway Island. 



Genus ADELOSINA d'Orbigny, 1826. 



Adelosina d'Orbigny (Type A. laevigata d'Orbigny), Ann. Sci. Nat., vol. 7, 1826, 

 p. 303. — Schlumberger, Bull. Soc. Zool. France, vol. 11, 1886, p. 544. 



Description. — Test in its early portion consisting of a large, later- 

 ally compressed proloculum, followed by a second chamber making 

 a complete coil and covering the exterior of the proloculum, later 

 chambers making a half coil, variously ornamented, most frequently 

 with longitudinal costae. 



ADELOSINA LAYSANENSIS Rhumbler. 



Plate 17, fig. 9. 



Adelosina laysanensis Rhumbler, Zool. Jahrb., Abteil. Syst., vol. 24, 1907, p. 50, 

 pi. 3, figs. 37, 38. 



Description. — Test elongate elliptical, more than twice as long as 

 broad, longitudinally ribbed, about 12 visible on the broad side of 

 the test; apertural end slightly or not at all produced, sometimes 

 contracted ; aperture with a single tooth. 



Length, 0.10 to 0.18 mm. 



Distribution. — This species was described by Rhumbler from shore 

 sands of Laysan, where it was found to be common. 



Genus BILOCULINA d'Orbigny, 1826. 



Biloculina d'Orbigny, Ann. Sci. Nat., vol. 7, 1826, p. 297 (Type B. bulloides 

 d'Orbigny). — H. B. Brady, Rep. Voy. Challenger, Zoology, vol. 9, 1884, 

 p. 139. 



Description. — Test in the adult, composed of chambers one-half 

 coil in length, in planes 180° from one another, only the two cham- 

 bers last formed visible from the exterior; aperture usually broader 

 than long, typically with a bifid tooth. 



As has already been noted in the early pages of the present part, 

 Biloculina is a genus derived from Quinqueloculina through Trilocu- 

 lina. In the complete series of stages shown by the microspheric 

 form of the species after the proloculum and usual second Cornuspira- 

 like chamber there is built a series of chambers in planes 144° from 

 53709°— Bull. 71, pt. 6—17 6 



