FORAMINIFERA OF NORTH PACIFIC OCEAN. 19 



base to which the foreign material is attached. There seems to be a 

 regular succession of forms from Astrorhiza, in which there is a central 

 chamber with many irregular openings to the tubular form open at 

 both ends and of indefinite length, thence to the chamber closed 

 usually except at a single point as Proteonina or with several apertures 

 as in Tlmrammina. This single-chambered form then leads to the 

 forms with a globular proloculum and an elongated chamber, but 

 undivided. Occasionally tests are found as in Rhabdammina discreta, 

 where there are external constrictions, but without complete divisions 

 within. 



Subfamily 1. ASTRORHIZIN^]. 



Test consisting usually of a tube open at both ends or in some 

 species of Astrorhiza with several tubes entering a central chamber; 

 in some species with the tube branching (Rhabdammina irregularis, 

 Rhizammina algaeformis, etc.). 



Included in this subfamily are five genera, Astrorhiza, Rhabdam- 

 mina, Marsvpella, Bathy siphon, and Rhizammina. With the ex- 

 ception of the first we know very little concerning the animal, excepting 

 for the material of which the test is made ; each consists of a simple or 

 branching tube open at the ends, except in some species of Astrorhiza, 

 where there are several tubes and a single central chamber. The 

 growth seems to take place by the addition of material at the open 

 ends of the tube, thus increasing the length. 



Genus ASTRORHIZA Sandahl, 1857. 



Astrorhiza Sandahl (type, Astrorhiza limicola Sandahl), Ofv. Svensk. Vet. Akad. 



Forh., vol. 14, no. 7, 1857, p. 299.— H. B. Brady, Rep. Voy. Challenger, 



Zoology, vol. 9, 1884, p. 230. 

 Astrorhiza-\- Rhabdammina (part) Eimer and Fickeet, Zeitschr. wiss. Zool., vol. 



65, 1899, p. 666. 

 Ammodiscus Carpenter and Jeffreys, Proc. Roy. Soc. London, 1870, p. 159 



(not Ammodiscus Reuss, 1871). 

 Arenistella Fischer and deFolin, Les fonds de la mer, vol. 2, 1872, p. 26. 

 Astrodiscus F. E. Schulze, II Jahr. Comm. wiss. Unt. deutsch. Meer in Kiel, vol. 



1, 1875, p. 113. 

 Exckelina Bessels, Jen. Zeitschr., vol. 9, 1875, p. 265. 



Description. — Test free, flattened or tubular, composed of sand or 

 mud loosely cemented ; chamber within connecting with the exterior 

 by the open ends of the tubes or by several definite apertures in the 

 flattened forms. 



Five species occur in the North Pacific, so far as is known. They 

 are typically cold-water species here, as also in the North Atlantic. 

 None of the species seem to be common so far as the material that 

 has been examined shows. 



