564 PROF. P, MARTIN DUNCAN ON MICRABACIA CORONULA. 
the other, the intervening space forming a canal when the septa 
are placed in normal apposition and the fractured surfaces of the 
synapticula are united. The synapticula are rarely continuous up 
an intermediate loculus, but are usually in continuous series, and 
the direction is well preserved (fig. 1). But this discontinuity inter- 
feres with the perfectness of the canals and permits them to com- 
municate. 
Figs. 1-3.—Structure of Micrabacia coronula. 
Fig. 1. A section of Micrabacia coronula, magnified, showing basaland septal 
synapticula. 
Fig. 2. Synapticula ending close above the basal synapticula, much magnified. 
Fig. 3. Side or marginal view, showing bifurcating coste terminating above 
in septa, much magnified. 
Sometimes the synapticula, when looked at from above, are 
slightly constricted ; but their length can never be appreciated from 
such a view, for only their tops are then seen. 
On tracing the synapticula, in fractured specimens, downwards 
in the lower parts of the interseptal loculi, they will be found 
usually to cease above the base (fig. 2), and to be succeeded in 
order by others, which are short and variable in shape. Those at 
the base are the bars seen between the coste at the base of the 
corallum. The spaces between these bars pass upwards into the 
more or less continuous canals just mentioned, and the bars are 
evidently synapticula. 
The synapticula are often large, rather high up in the loculi, and 
they cover much of the surface of the septa, but there is much 
variation in their development in different individuals. 
