The quadrate is invariably a conspicuous bone and movably articulating with the cranium and by a special process with the pterygoid.
Opisthosoma was movably articulated to the prosoma, and consisted of from eight to ten segments furnished with movable lateral plates, the anal segment being overlapped dorsally by a laminate expansion of the preceding segment.
Dentary movably attached to the tip of the articular bone of the mandible.
Viperidae.-The maxillaries are very short, movably pivoting upon the prefrontals and also attached to the ectopterygoids, so that they can be erected together with the large poison fangs, which, besides reserve teeth, are the only maxillary teeth.
The Anomaluridae are characterized by having rooted cheek-teeth with shallow transverse enamel-folds, the two halves of the lower jaw movably articulated in front, very small post-orbital processes to the skull, and the presence of two rows of scales on the under surface of the base of the tail (figs.