Maxillary horizontal; pterygoid not reaching quadrate or mandible: Amblycephalidae.
The pterygoids are delicate slender slips of bone attached to the hinder border of the palatines, and supported externally by, and generally welded with, the rough pterygoid plates of the alisphenoid, with no pterygoid fossa between.
Eo, Opisthotic. prp, Pterygoid process of sphe eu, Eustachian tube.
In the skull the tympanic bulla is hollow, the pterygoid fossa shallow and the zygomatic arch slender, with a rudimentary jugal bone.
No ectopterygoid pterygoid not extending to quadrate; no supratemporal or squamosal; prefrontal forming a suture with nasal; coronoid present; vestiges of pelvis present.
Snakes possess teeth in the maxillaries, mandibles, palatine and pterygoid bones, sometimes also in the intermaxillary; they may be absent in one or the ether of the bones mentioned.
Maxillary horizontal; pterygoid reaching quadrate or mandible.
St.) is directed downwards and tapers out into a thin, partly cartilaginous, strand, which originally extended to the inner corner of the articular portion of the mandible, but on its long way comes to grief, being squeezed in between the pterygoid and quadrate.
The third sub-family is that of the Microtinae, or voles, which are distributed all over Europe, Northern Asia and North America, and are characterized by the tympanic bulla of the skull being filled with honey-combed bony tissue, the small size of the infra-orbital foramen, and the deep pterygoid fossa on the palatal aspect.