640 
THE VOYAGE OF H.M.S. CHALLENGER. 
must either retain their present arrested dimensions, or else rupture the delicate balloon- 
like envelope, and continue their growth by adding chambers to the spiral or annular 
series. It appears probable that the latter is what actually takes place, for in bottom 
dredgings in which the species occurs there are always abundance of shells, the contour 
and structure of which more nearly resemble the Rotalian portion of Cymbalopora bulloides 
than the normal shell of its ally Cymbalopora poeyi. Such specimens are to all appear- 
ance living and growing, and sometimes bear traces at the edges of the previous existence 
of a balloon-like chamber. 
Of the close relationship of these forms there can be no doubt, but a question arises as 
to the degree of importance to be attached to the peculiar characters of Cymbalopora 
bulloides. Moebius treats the inflated final chamber as a generic distinction ; but it may 
be pointed out that similar structures are not unknown in other genera. Pulvinulina 
lateralis, for instance, has a distended final segment with large bordered pores on its 
distal face, which appears to be analogous, morphologically, to that of the present species 
(PL CYI. fig. 2 b). Under these circumstances, I have only employed the term Tretom- 
phalus provisionally, and in a subordinate sense, for the pelagic variety. 
The geographical distribution of Cymbalopora bulloides follows that of its congeners, 
but the number of localities at which it has been found is comparatively small. Surface 
gatherings were obtained off Zamboanga, Philippine Islands, and at several points in the 
neighbourhood of the Sandwich Islands. Bottom specimens have been collected in the 
North Pacific, — off the Honolulu Reefs : in the South Pacific, — off the Admiralty 
Islands, the New Hebrides, and Raine Island, and at numerous localities around the 
Fiji group : in the Indian Ocean, — off Mauritius (Moebius), and on the shores of 
Madagascar : and in the North Atlantic, — from the shore-sands of Cuba and Hayti 
(d Orbigny), and off Bermuda. 
Discorbina, Parker and Jones. 
Rotalites, Lamarck [1801], Defrance, Blainville. 
Rotalia, pars, Lamarck [1804], d’Orbigny, Munster, Roemer, Mickelotti, Parker and Jones, 
Morris and Quekett. 
Discorbis, Discorbites, Lamarck [1804], Defrance, Blainville, Berthelin. 
Rotulites, Defrance [1824], Blainville. 
Rosalina, pars, d’Orbigny [1826], Schultze, Parker and Jones, Reuss. 
Anomalinct, pars, d’Orbigny [1826], Reuss. 
Trochulina, d’Orbigny [1826]. 
Valvulina, pars, d’Orbigny [1839], Reuss. 
Asterigerina, d'Orbigny [1839], Reuss, Egger, Costa, Morris and Quekett, Karrer, Terquem. 
Rotalina, pars, Reuss [1845], Williamson, Alcock, Parfitt, Terquem. 
Discorbina, Parker and Jones [1862], Carpenter, Brady, Reuss, M. Sars, Karrer, Giimbel, Miller 
and Vanden Broeck, Schultze, Robertson, Winther, Norman, Hantken, Siddall, Shone, 
Marsson, Wright, Moebius, Seguenza, Terrigi. 
