FORAMINIFERA OF NORTH PACIFIC OCEAN. 



25 



There is a considerable variation in this species along certain lines. 

 Typically there are three arms, but there are occasionally four or 

 five, these specimens usually being rare. However, at station D4337, 

 off San Diego, California, there was obtained a considerable series 

 of specimens of this species and among these examples with four 

 or even five arms were rather common. In the matter of tex- 

 ture of the wall there is also a considerable variation, partly due 



Figs. 8-10.— Rhabdammina abyssorum. 8a, front view; b, end view of one arm of the smoother 

 form from deep water, x 10; 9, front view of a shallow water specimen from the coast 

 of Japan, x 25; 10, central portion of a specimen with four arms, x 15. 



to bottom conditions it would appear from the material examined. 

 The specimens from shallower water are more apt to be constructed 

 of coarse sand grains, figure 9, while those from deep water where 

 such materials are lacking are made of much finer grains with more 

 or less mud and often contain Globigerina or other tests in the wall. 

 This species has been usually found in deep water, all but four stations 

 being in water more than 600 fathoms deep. 



