File:The Quarterly journal of the Geological Society of London (13889274410).jpg

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PItOF. p. MARTIN DTJ^'CAN OX MICEABACIA COROXFLA.
the other, the interyening 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.
Pigs. 1-3. — Structure o/ Micrahacia coronula.
1.
3.
Fig. 1. A section of Micrahacia coronula, magnified, showing basal and septal
synapticula.
Pig. 2. Synapticula ending close above the basal synapticula, much magnified.
Pig. 3. Side or marginal ricTr, showing bifuicating costte terminating aboTe
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 (tig. 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 costae 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