FOBAJMINIFEBA OF THE NOKTH PACIFIC OCEAN. 13 



half to two volutions; chambers increasing rapidly in size as added, 

 usually 5 to 6 visible in side view, sutures much depressed giving a 

 lobulated contour; wall reticulate, often with broken spines; aper- 

 ture large, an arched opening at the base of the chamber. 



Diameter up to 1 mm. 



Distribution. — Brady records this species in the North Pacific from 

 the following Challenger stations, Honolulu coral reefs, 40 fathoms; 

 station 206 in 2,100 fathoms, 214 in 500 fathoms, and 224 in 1,850 

 fathoms. Bagg records it from IS Albatross stations off the Hawaiian 

 Islands, depths ranging from 104 to 1,544 fathoms. I have had 

 material from numerous Albatross stations between San Francisco 

 and the Hawaiian Islands, depths ranging from 323 to 2,615 fathoms. 

 It has occurred at a great number of stations of the Nero wherever 

 those soundings were below 2,000 fathoms across the Pacific and 

 especially between Yokohama and Guam where I have record of its 

 occurrence at 40 stations. It has also occurred in the material from 

 the soundings of the Alert and Tuscarora and off Japan in the Albatross 

 work as well as off the Galapagos Islands. Altogether it seems to be 

 well distributed in the North Pacific and to occur abundantly at 

 many stations. 



The planospiral arrangement of the chambers in this species will 

 distinguish it from the others of the genus. There is some consider- 

 able variation in the closeness of the coiling in various specimens. In 

 old-age specimens there is a tendency to reduce the size of the last- 

 formed chamber and to make it less high and of smaller diameter 

 than the preceding one. 



Genus ORBULINA d'Orbigny, 1839. 



Orbulina d'Orbigny (type, 0. universa d'Orbigny), in De la Sagra, Hist. Fis. 

 Pol. Nat. Cuba, 1839, Foraminiferes, p. 3.— H. B. Brady, Rep. Voy. Chal- 

 lenger, Zoology, vol. 9, 1884, p. 606. 



Description. — Test composed of several Globigerina-like chambers, 

 rapidly increasing in size as added, finally entirely surrounded by the 

 adult chamber which is spherical, with numerous small pores and one 

 large circular orifice, or occasionally more than one; wall reticulated, 

 in living condition with long, fine spines. 



There has been much discussion in the past in regard to the posi- 

 tion of Orbulina and its relation to Globigerina. It seems best now 

 that something is known of the development to recognize Orbulina 

 as a genus derived from Globigerina ancestry, the adult final chamber 

 inclosing the earlier ones being a good generic character. It is com- 

 parable to certain of the Miliolidse where a similar inclosing of the 

 earlier developed chambers takes place. 



In Orbulina there seems to be a process of resorption by which the 

 interior chambers disappear in the adult specimens, the smaller, 

 thinner specimens having such included chambers, whereas they 

 almost never are found in large well-developed specimens. 



