88 
Williamson on Fmijasina. 
which divide the different segments of each convolution (fig. 
2 h and d), but they do not occur in the peripheral margin 
{I f and 6 <?), or in the spiral septum (fig. 2 e). At the upper ex- 
tremity of the shell similar, but larger, pits are seen both on the 
flat truncated surface {Ida') and on the sides intervening be- 
tween it and the upper portions of the segments (6 h). On 
making a series of sections of the shell we learn that these pits 
are the external orifices of a curious system of intra-septal 
canals and spaces, ramifying in its interior. 
Fig. 2 represents a thin superficial section of the inferior flat 
surface, viewed as a transparent object. Thus examined, the 
conditions are reversed. The foramina in the parietes of the 
hollow segments tend to intercept the light and look dark, 
whilstjthe solid calcareous septa are translucent and transmit 
it freely. This section was made a little below the peripheral 
margin and parallel with the points a, a in fig. 1. 
The walls of the segments (2 d) exhibit the ordinary forami- 
nated aspect, and the segments themselves are arranged in 
the usual spiral manner. The spiral contour is lost in the 
centre of the section, owing to the circumstance that it there 
becomes very thin, and passes under the central cells which 
are placed a little above the level of those which surround 
them. In the radiating septal lines are seen numerous small 
orifices (2 Z)), which open by means of short canals (fig. 5A, A') 
into the interseptal spaces immediately above them. As 
already observed, these orifices do not exist in the spiral sep- 
tum (2 e), but here and there even this superficial section ex- 
hibits traces of deep-seated canals passing through the septum 
and uniting the orifices belonging to contiguous convolutions 
(2 c). In this portion of the shell the apertures are usually 
in single rows ; but towards the exterior of the outer segments 
we sometimes see them arranged in pairs (2 d\ It is of 
course the external surface of the base of the shell that is re- 
presented in the drawing. 
On making a second section parallel to the last, but a little 
above the peripheral margin, in the plane of the points 1 Z>, Z>, 
we have the appearance presented by fig. 3. The drawing 
represents this section as seen when viewed in the opposite 
direction to the last, viz. looking at its upper or inner surface, 
and towards the base of the shell — some of the foraminated 
parietes of which are still preserved. 
We now perceive that there exists a number of large branch- 
ing intra-septal tubes and passages, which commence at the 
innermost segments and proceed in a radiating manner towards 
the periphery. As each of these tubes emerges from the 
septum separating two contiguous segments, and reaches the 
spiral one intervening between two convolutions, it exhibits a 
