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THE VOYAGE OF H.M.S. CHALLENGER. 
margin blunt or rounded. The ornament likewise varies with age, being more distinctly 
linear and geometric in the early stage (fig. 15), thicker and less regular in old specimens 
(fig. 16). 
So far as at present known, Pulvinulina favus is exclusively a Pacific species ; indeed, 
but for a few specimens obtained at Station 224, about eight degrees north of the equator, 
it might be said to be peculiar to the South Pacific, inasmuch as the remaining nine 
Stations at which it has been found lie between the equator and lat. 42° 43' S. It is a 
deep-water organism, with a bathymetrical range extending from 1375 fathoms to 2600 
fathoms. 
Rotalia, Lamarck. 
Nautilus, pars, Linni [1767], Walker and Boys, Adams, Montagu, Maton and Rackett, Parkinson, 
Pennant, Dillwyn, Turton, &c. 
Rotalia, Lamarck [1804], d’Orbigny, Fleming, Bronn, Michelotti, Hagenow, Macgillivray, 
Thorpe, Parker and Jones, Reuss, Carpenter, Sowerby, Brady, M. Sars, Schwager, Karrer, 
Schulze, &c. 
Discorbida, Lamarck [1816]. 
Streblus, Fischer [1819]. 
Gyroidina, d’Orbigny [1826], Bronn. 
Turbinulina, pars, d’Orbigny [1826]. 
Galcarina, pars, d’Orbigny [1826], Carpenter, Parker and Jones, Brady. 
Rotalites, Defrance [1827]. 
Asterigerina, pars, d’Orbigny [1839]. 
Rotalina, pars, d’Orbigny [1839], Reuss, Czjzek, Bomemann, Williamson, Karrer, Seguenza, 
Alcock, Hantken, Parfitt, Schlicht, Stewart, Terquem, Norman, Martonfi, &c. 
Rosalina, pars, d’Orbigny [1839], Reuss, Costa, Egger, Karrer, Schlicht. 
Discorbis, Macgillivray [1843]. 
Faujasina, Williamson [1853]. 
As compared with the collateral genera, Planorbulina and Pulvinulina, the true 
Rotalia form but a small series ; and the range of morphological variation which they 
exhibit, so far as the more conspicuous features of the test are concerned, is embraced 
within much narrower limits. 
The general conformation of the shell is that of a turbinoicl spire, which in its typical 
phase ( Rotalia beccarii ) is nearly equally convex on the two faces. Some varieties, 
however, present a convex, or even conical, superior face, whilst the inferior side is flat 
(. Rotalia nitida ) ; and on the other hand, there is a more important set of forms, in which 
the superior face is approximately flat and the inferior highly convex (Rotalia soldanii, 
Rotalia .schroeteriana, &c.) — between the two extremes every gradation of contour is 
exemplified in the series. 
The normal “ Rotaliform ” arrangement of the chambers, by which the whole of 
the segments are visible on the superior side of the test, those of the final convolution 
only on the inferior, is tolerably constant throughout the genus, the only marked 
