FORAMINIFERA OF THE ATLANTIC OCEAN 87 



Test free, subglobular; early chambers rotaliform, numerous, 

 rather coarsely perforate, forming a cap to which is attached a large 

 final "balloon-chamber," subspherical, with coarse perforations on 

 the ventral side, and within, a "float-chamber" with a single opening 

 at the base, from which a tubular neck projects inward; color of the 

 early chambers dark brown, the large chamber colorless. 



Diameter up to 0.40 mm. 



From the synonymy given above, it will be seen that there are 

 man}^ records for this species which apparently lives on the bottom 

 or attached during its earlj^ stages, then develops the float-chamber 

 and becomes free and pelagic. The empty test may float for a con- 

 siderable time as Woodward records it from the south side of Cape 

 Cod off Marthas Vineyard. I have not found it in any Albatross 

 bottom samples from this region, but it is possible that it may be 

 driven in as is the Gulf-weed, Physalia, and other typical Gulf- 

 stream species with favorable winds. I have collected dozens of 

 Physalia in Vineyard Sound under such conditions, and it may be 

 that at such times tests of Tretom/phalus may be brought in. Its 

 typical habitat however is in tropical waters. In the Indo-Pacific 

 it also occurs, and is accompanied by other species. 



Moebius (1880) has given an account, and figures of the structure 

 of this species as have Earland (1902) and Heron-Allen (1915). In 

 my Tortugas paper (1922) I have given a series of notes on the studies 

 of this species at the Tortugas Laboratory which are copied here. 



d'Orbigny originally described this species as Rosalina hulloides in 

 the Cuban monograph, his specimens being from Cuba and Haiti. 

 By most authors it has been assigned to Cymbalopora, but Moebius 

 in 1880 erected the genus Tretomphalus for this species, and in view 

 of the structures revealed by later studies it seems best to use this 

 name. The Cymbalopora millettii of Heron- Allen and Earland 

 should also be known as Tretomphalus millettii. These two species 

 have had considerable attention from various authors, especially 

 Moebius, Murray, Brady, Earland, and Heron-Allen. 



Tretomphalus bulloides occurs both as a pelagic species and as a 

 bottom form. This fact has led to various theories concerning its 

 life history. From what is known of the pelagic form, it undoubtedly 

 becomes empty and sinks to the bottom. Whether or not all the 

 bottom specimens may thus be accounted for can not be stated with 

 any degree of certainty. It seems possible that the enlarged "balloon- 

 chamber" is developed from a bottom-living form, as many species 

 adapted to a pelagic life develop a more or less inflated final chamber 

 with large pores. These evidently allow free passage of the proto- 

 plasm, which, being extended and containing gases, floats the test 

 without difficulty. Sir John Murray, while on the Challenger, ob- 

 served living specimens of Tretomphalus bulloides, filled with "flagelli 

 2305—31 7 



