312 FORAMINIFERA OF THE CRAG. 



Characters. — Shell orbicular, formed of from three to four revolutions of a 

 spire, each consisting of six or seven chambers. Aboral surface more or less 

 trochoid ; tl^e other (oral or inferior) face subconvex, often excavated at the 

 umbilicus ; formed of about six triangular chambers extending from the 

 periphery to the umbilicus. Margin blunt, scarcely angular. Foramina 

 numerous and conspicuous over every part of the shell. 



Between the neat, well-defined, highly trochoid shell figured by d'Orbigny and 

 the somewhat clumsy, indefinite examples of the same species found in the Crag 

 there seem, at first sight, to be few characters in common ; yet there need be no 

 hesitation in regarding them as the same form. It is rare under any circum- 

 stances to meet with specimens so distinct in all external characters as the 

 figures in the " Vienna Basin " monograph indicate ; and, on the other hand, the 

 few which have been found in the Crag (from Sutton and Sudbourne), though of 

 average size, have their structure obscured either by the thickening of the shell 

 wall from age, or by the mechanical eff'ect of attrition. 



Occurrence. — Truncatulina Haidingeri is not of frequent occurrence in the 

 recent condition, though it has a wide range geographically. It has been found 

 at various depths down to 1776 fathoms (' Challenger' Report) and 2140 fathoms 

 ('Gazelle'). 



In the fossil condition it appears to be more common. Specimens have been 

 found in the Neocomian (Bargate beds of Surrey) ; the Eocene (London Clay and 

 Calcaire Grossier) ; the Miocene of Malaga, Italy, Vienna, and Muddy Creek 

 (Victoria) ; and the Pliocene of Italy, Garrucha, and St. Erth. In the Coralline 

 Crag we have found examples in nearly every zone examined. 



5. Truncatulina Ungeriana (d'Orbigny), 1846. Plate II, figs. 11, 12. 

 Part I, 1866, Appendices I and II, Tables, No. 79. 



AmmonisB univolutse, Soldani, 1780, Saggio Orittogr., [>. 103, pi. iii, figs. 22, h, 



H,I. 

 HammonisB Univolutse, Soldani, 1798. Testaceographia, vol. ii, App.,p. 139, pi. iii, 



figs. 22 h, H, I. 

 EoTALiA (Turbinulina) Sienneksis (?), d'Orb., 1826. Ann. Sci. Nat., vol. vii, 



p. 275, No. 50. 

 EoTALiNA Ungeeiana, d'Orb., 1846. For. Foss. Vieun., p. 157, pi. viii, figs. 16 



—18. 



— SEMiPUNCTATA, Bailey, 1851. Smithsonian Contrib., vol. ii, art. 3, 



p. 11, figs. 17—19. 



— Ungeeiana, Reuss, 1851. Zeitsch. geol. deutsch. Ges., vol. iii, p. 70. 



— — JSomemann, 1855. Ibid., vol. vii, p. 341, pi. xvi, fig. 5. 



