152 Prof \ Macalister , Variations in the ossification , etc. 
but may be reduced to three groups, lambdoidal, intermediate and 
asterial. 
The angle of the lambda may be formed by a single bone 
or of a pair of lambdoid bones which differ from the preinter- 
parietal in the depth to which they penetrate into the squama. 
By overgrowth they sometimes seem to push the preinterparietal 
element very hardly, but there is generally little difficulty in 
the way of distinguishing them. Outside these there are often 
paralambdoid bones, single, paired or multiple; occasionally a pair 
of paralambdoids may exist while the angle is preinterparietal. 
About the middle of the lambdoidal suture on each side there 
is a more or less conspicuous reentrant angle on the hinder edge 
of the parietal into which a projecting angle of the occipital 
projects. This is the angulus intermedius. On the whole skull 
this lies along the line of that indefinite rounded ridge that forms 
the boundary between the medial strip of skull-roof and the 
lateral skull-wall, which continues from the frontal tuber through 
the parietal tuber, and here crosses the lambdoid suture to end in 
the linea nuchse suprema. The parietal notch probably owes its 
existence to the unequal growth of the twin centres of that bone 
the limits of whose posterior territories it marks. On the occipital 
it corresponds nearly to the limit between the preinterparietal and 
the interparietal. At this spot an angular bone is very commonly 
developed, often flanked medially by one or more metangular and 
distally by one or more parangular. 
The third region at which wormian bones may be found is the 
asterion or point of confluence of the parietal, mastoid, inter- 
parietal and supraoccipital bones. Here there is often a galaxy 
of ossicles, sometimes only an asterial or a metasterial bone, 
flanked perhaps by others not belonging primarily to the lambdoid 
suture, but to the occipitomastoid or parietomastoid. 
To one or other of these types the larger sutural bones may 
be referred. There are also minuter ossicles of another category 
representing detached portions of sutural teeth separately ossifying 
and often embedded, not penetrating the whole thickness of the 
bone. 
