MILIOLIDA. 7 
Subgenus—Tritocunina, D’ Orbigny. 
General characters.—Having three chambers visible externally ; either cariate or 
rounded. 
1. Trinocunrna TRIcARINATA, D’Orbigny. Plate III, figs. 33, 34. 
TRILOCULINA TRICARINATA, D’Orb., 1826. Modéle No. 94; Ann. des Sc. Nat., vol. vii, 
p. 299; No. 7. 
— _ Brady, 1864. Trans. Linn. Soc., vol. xxiv, p. 466, pl. 48, 
fig. 3. 
MiLiota (TRILOCULINA) TRICARINATA, Parker and Jones, 1865. Phil. Trans., vol. elv, p. 409, 
pl. 15, fig. 40. 
Characters.—Shell elliptical, angular, having the chambers produced at the margins 
so as to form three carimate edges. Aperture at the end of the outermost chamber. 
Length, jth inch. 
Triloculina trigonula, Lamarck, being regarding as the best sub-type of the Trilo- 
culine MWiliole, the sub-variety 7. tricarinata bears the same relation to it that Bzloculina 
depressa does to B. ringens ; that is to say, it is the form which assumes sharp angular 
margins, 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 Foraminifer; for, though it 
occurs in localities far distant from each other, it is seldom found in any abundance. 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, 32. 
VERMICULUM OBLONGUM, Montagu, 1803. Test. Brit., p. 522, pl. 14, fig. 9. 
TRILOCULINA OBLONGA, D’Orb., 1825. Modéle No. 95; Ann. Sc. Nat., vol. vii, p. 300, 
No. 16. 
— a Id., 1839. Foram. de Cuba, p. 175, pl. 10, figs. 3-5. 
