A NEW FORAMINIFER COMJ^IENSAL ON CYCLAMMINA. 



By Joseph A. Cushman, 



OJ the Boston Society of Natural History. 



Specimens of Cydammina are occasionally found which, instead of 

 being bilaterally symmetrical, have the last few chambers much 

 extended on one side. Such specimens have a deep depression in the 

 umbilical region of the same side. These have been noted in the 

 material collected by the United States Bureau of Fisheries steamer 

 Albatross from the northeastern coast of the United States in my 

 examination of that material, but without a discovery of the cause. 

 On examining material from Albatross station D2213 a number of 

 specimens of Cydammina with this character were noted, and a further 

 search revealed the cause tor the abnormal form. 



It is caused by the attachment of a single-chambered species of 

 foraminifera to the outside of the test of the specimen of Cydammina 

 and the further growth of the test about this. When the attached 

 form falls away it leaves the resulting space unoccupied and the 

 resulting depression. So far as the material shows this seems to be a 

 one-chambered species with a chitinous wall somewhat arenaceous m 

 parts but with little variation in size. 



The position as shown in plate 25, figure 4, is at the edge of the 

 aperture when the attachment is made. Later, by the continued 

 growth of Cydammina this position becomes more nearly umbilical. 

 There is as a rule but a single attached specimen, but two may be 

 attached, either on one side as shown in plate 25, figure 1, or there 

 may be one on each side, as in figure 3. This at once suggests that 

 little or nothing is known of the life habits of Cydammina except that 

 it is a heavy, bottom-living form. If the attached specimens were 

 always on one side only it would suggest that Cydammina might live 

 on its side, but with specimens with both sides occupied this does not 

 hold. Cydammina might lie Vv'ith its appertural face uppermost 

 which would allow opportunity for the pseudopodia both of the at- 

 tached form and of itself to rise easily to the surface of the bottom 

 ooze. At any rate, Cydammina seems too heavy to be a form with 

 any great freedom of movement. 



Proceedings U. S. National Museum, Vol. 56— No, 2290. 



101 



