MILIOLIDA. 



Subgenus — Triloculina, D' Orhigny. 



General characters. — Having three chambers visible externally ; either carinate or 

 rounded. 



1. Triloculina tricarinata, B' Orhigny. Plate III, figs. 33, 34. 



Triloculina tricarinata, B'Orb., 1826. Module No. 94; Ann. des Sc. Nat., vol. vii, 

 p. 299, No. 7. 

 — — Brady, 1864. Trans. Linn. Soc, vol. x.\iv, p. 466, pi. 48, 



fig. 3. 

 MiLioLA (Triloculina) tricarinata, Parker and Jones, 1865. Phil. Trans., vol. civ, p. 409, 



pi. 15, fig. 40. 



Characters. — Shell elliptical, angular, having the chambers produced at the margins 

 so as to form three carinate edges. • Aperture at the end of the outermost chamber. 

 Length, ^'gth inch. 



Triloculina trigonula, Lamarck, being regarding as the best sub-type of the Trilo- 

 culine Miliolce, the sub-variety T. tricarinata bears the same relation to it that Biloculina 

 depressa does to B. ringens ; that is to say, it is the form which assumes sharp angular 

 marghis, instead of the rounded contour of the sub-type. Mr. Wood found it large 

 and rare at Sutton. The true sub-typical form, though much more widely distributed 

 than this variety, we have nowhere met with in the Crag. 



Triloculina tricarinata can scarcely be called a common Foramiuifer ; for, though it 

 occurs in localities far distant from each other, it is seldom found in any abimdance. We 

 have one or two specimens from the British Seas ; in deeper water and in more northerly 

 latitudes small specimens are frequent ; but perhaps it attains its maximum size and 

 frequency on the Australian coast. Geologically, its occurrence is, so far as we know, 

 confined to the Tertiary formations, commencing in the Eocene deposits of Grignon, in 

 the Paris Basin. 



2. Triloculina (Quinqueloculina) oblonga, Montagu. Plate III, figs. 31, 33. 



Vermiculum oblongum, Montagu, 1803. Test. Brit., p. 522, pi. 14, fig. 9. 

 Triloculina oblonga, UOrb., 1825. Module No. 95; Ann. Sc. Nat., vol. vii, p. 300, 

 No. 16. 

 — — Id., 1839. Foram. de Cuba, p. 175, pi. 10, figs. 3-5 



