688 



Transactions of the Society. 



Fig. 13 a, b, c. — Shell oval, sub-convex above, depressed below, 

 the upper surface formed of early chambers indistinctly indicated, 

 the three later chambers being prominent. On the inferior surface 

 all the chambers are prominent, the three latest being swollen. A 

 secondary aperture on the anterior surface of the terminal chamber. 

 (Septeuil.) 



P Fig. 14 a, b, c. — Shell circular, compressed on both sides, rounded 

 circumference, with a nucleus. The superior surface formed of 



12 h 



40 

 l 



. _ 



J3 



40 



l * 



24 

 1 



strongly marked chambers with deep sutural lines. On the inferior 

 surface the outer chambers prominent, the inner triangular and well 

 marked. Secondary aperture, a. slit on the anterior surface of the 

 last chamber. (Septeuil.) 



Terquem adds that the species is formed of two series of cham- 

 bers in juxtaposition. The upper series, which encroaches upon 

 the lower, frequently has a specialised aperture situated in the 

 middle of the terminal chamber. The lower, which exceeds the 

 upper in development, shows live chambers, whilst the upper has 

 but four, occupying the same area. 



