148 
THE VOYAGE OF H.M.S. CHALLENGER. 
Spiroloculina it is not uncommon to find specimens of which the central portion is some- 
what thicker than the remainder of the shell, which is the result of a non-symmetrical 
or Miliolina-like arrangement of the earliest segments. Deep-sea specimens of Spirolo- 
culina tenuis are often in this condition. Sometimes the successive chambers embrace the 
preceding ones on the same side, in part or almost entirely, and the test becomes slightly 
concave, whilst retaining otherwise its nearly symmetrical contour. Lastly, there are 
certain forms in which the later segments individually occupy less than one-half of a 
convolution, and these lead by insensible degrees to the genus Hauerina. Such 
intermediate conditions are a frequent source of difficulty to the systematist, though 
they furnish interesting links connecting the subordinate types. 
The genus Spiroloculina most affects the shallow margins of temperate and tropical 
seas. From the littoral zone to a depth of five or six hundred fathoms it is comparatively 
abundant, hut at greater depths the number of species diminishes, and beyond a thousand 
fathoms only the small thin variety ( Spiroloculina tenuis ) is usually met with. It makes 
its first appearance, geologically, in the Lower Lias clays of Warwickshire (Parker and 
Jones) ; it is found in the Middle Lias of Essey-les-N ancy (Terquem and Berth elin) ; 
in the Upper Lias of the neighbourhood of Banbury (Walford), and subsequently in 
microzoic strata of almost every age. 
Spiroloculina planulata, Lamarck, sp. (PI. IX. fig. 11, a.b.). 
“ Frumentaria Sigma et Rliombos,” Soldani, 1795, Testaceographia, yol. i., part 3, p. 299, pi. 
civ. fig. kk. 
Miliolites planulata , Lamarck, 1805, Ann. du Museum, vol. v. p. 352, No. 4. — 1822, Anirn. s. 
Vert., vol. vii. p. 613, No. 4. 
Miliola planulata, Defrance, 1824, Diet. Sci. Nat., vol. xxi. p. 68. 
Spiroloculina depressa, d’Orbigny, 1826, Ann. Sci. Nat., vol. vii. p. 298, No. 1. — Module, 
No. 92. 
,, badenensis, Id., 1846, For. Foss. Vien., p. 270, pi. xvi. figs. 13-15. 
,, dilatata, Id. Ibid., p. 271, pi. xvi. figs. 16-18. 
„ depressa, var. rotundata, Williamson, 1858, Rec. For. Gt. Brit., p. 82, pi. vii. 
fig. 178. 
„ planidata, Jones, Parker and Brady, 1866, Foram. Crag, p. 15, pL iii. 
figs. 37, 38. 
In dividing the Spiroloculince into specific or varietal groups Parker and Jones 
adopt Lamarck’s name, as the earliest, for the simple complanate forms with non- 
limbate sutures and without surface-ornament. To this “ species ” they refer the 
Spiroloculina depressa of d’Orbigny (Modele, No. 92) and the Spiroloculina depressa, 
var. rotundata of Williamson. The specimen figured by the latter author as the 
typical Spiroloculina depressa is referred by them to Spiroloadina limbata, 
d’Orbigny. 
I am not prepared to suggest any better mode of treatment. Any lines of separation 
